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LA-61 72-MS Informal Report UC-34a Reporting Date: November 1975 Issued: January 1976

CIC-14 REPORT COLLECTION REPRODUCTION COPY

Metallic Hydrogen:

A Brief Technical Assessment

L. A. Gritzo N. H. Krikorian

—L Contributors

D. T. Vier A. T. Peaslee, Jr.

)

} alamos scientific laboratory of the university of California 10s ALAMOS, NEW MEXICO a7545

\ An Affirmative Action/Equal Opportunity Employer

uNITEO STATES ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION CONTRACT W.7405.ENG. 36 In the interest of prompt distribution, this report was not edited by the Technical Information staff.

This work was supported by the DoD Defense Advanced Research Projects Agency. The views and conclusions contained in this report are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Defense Advanced Research Pro- jects Agency or of the United States Government.

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an? mformattom apparatus, LWXIuct, w D,,JWSJ di~lo,~, or rrr.ramt. that its use would not irifrlnce pri..tely owned rights. METALLIC HYDROGEN:

A BRIEF TECHNICAL ASSESSMENT

L. A. Gritzo and N. H, Krikorian

Contributors

D. T. Vier and A, T. Peaslee, Jr.

ABSTRACT

A brief technical assessment of the status of international research on metallic hydrogen is presented. Research methods are outlined; published work in the USSR, the US, and several other countries is reviewed. A prognosis is given for metallic hydrogen. Potential military applications and future research requirements are discussed, A bibliography is included.

1. INTRODUCTION

Chemical classification of elements ity; it could be expected to have some un- places those with a single outer (valence) usual properties. electron, i.e., a single electron in the Molecular hydrogen exists as a gas un- first unfilled shell, into a category call- der normal conditions. It can be liquefied ed alkali metals. This category includes at about 20”K through cooling at atmospher- lithium, potassium, sodium, etc., in which ic pressure. It will form a solid at 14°K the bonding of the valence electron to the with a complex crystal structure. Solid atom is weakened by the presence of addi- molecular hydrogen is a low-density (about tional electrons in interior shells. Hy- 0.09 g/cm3) dielectric (electrical non- drogen (H) is placed in the alkali metals conductor) material . category by default, since the valence elec- Since about 1935, numerous theorists tron is the only electron present in the have postulated the existence of an addi- neutral atom. The first electronic shell tional solid state for hydrogen, the metal- of an atom is filled only when exactly two lic state. In the metallic state, the atoms electrons are present. There is thus a would no longer exist as diatomic molecules. strong tendency for hydrogen atoms to exist Instead, they would be considered as a reg- paired as diatomic molecules (H2). Although ular array of protons embedded in a sea of the hydrogen atoms form diatomic molecules free-moving electrons. Many calculations with strong internal bonding forces, the have been made that indicate a degree of molecules experience only very weak forces stability for this type of atomic hydrogen in interactions with each other. Hydrogen structure. However, the computed interatom- is unique among the elements in its simplic- ic distances required for stability in the

1 atomic form are considerably less than those necessary to resolve existing questions will observed for the molecular form. In order be discussed. to achieve the compact atomic form, it is

believed that a large external pressure is II. THE WORLD-WIDE METALLIC HYDROGEN EFFORT required to be exerted on the molecular Both theoretical and experimental

form. The present literature indicates research has been conducted on molecular significant disagreement on the magnitude and atomic hydrogen. In the following text, of the pressure required to obtain the several research methods that have been used molecular-atomic solid transition. The d“ s- or proposed will be reviewed, The review is agreement appears to arise from both the followed by a discussion of work that has current lack of knowledge regarding the been done in the USSR, in the US, and in

response of hydrogen molecules to such other countries. external forces, and the insufficiencies in A. Research Methods

the mathematical models used to describe Nearly all experimental work has been systems of atoms and molecules. oriented toward the production of very high

Two important properties have been pressures and the application of these pres- postulated for the metallic form. The first sures to molecular hydrogen and deuterium. of these is metastability, i.e., retention The work generally falls into two major of the metallic form (produced at low tem- categories, dynamic and static. perature and under high pressure) after the The dynamic technique is exemplified by

pressure is reduced and the temperature is the work of Fowler at the Los Alamos Scien- raised. The second is superconductivity at tific Laboratory (LASL) and of Hawke at the temperatures far above that of ordinary Lawrence Livermore Laboratory (LLL). Hawke’s superconductors (about 15”K), Most re- description of the technique is:l searchers today expect that a molecular- Figure 1 shows a cross section of the experimental apparatus. An initial mag- atomic transition will occur in hydrogen. netic field is generated by use of a pair Such transitions have been observed in the of coils and a capacitor bank. The magnetic field diffuses through a stainless- USSR for other crystalline materials (e.g., steel liner surrounded by high explosive. salt, sulfur, silica and alumina). Many When the diffused magnetic field is close to its peak value, the high explosive is researchers question the postulated meta- detonated and the liner is cylindrically stability of the metallic form, especially imploded. The implosion compresses the magnetic flux and increases the magnetic at temperatures higher than the melting field intenkity, During the flux cumula- point of solid molecular hydrogen. Corres- tion, eddy currents generated in the sample tube and liner interact with the pondingly, most researchers will admit the magnetic field and exert an outward pres- possibility of the metallic form being sure on the liner and an inward pressure on the sample tube. superconducting, but many question the postulated high critical temperature (the Pressures up to about 4 Mb have been ob- temperature at which it would cease being tained with this method; the duration of a superconductor). the high-pressure pulse is very short The potential value of metallic hy- (submicro-second) . Diagnostic equipment drogen hinges on a favorable outcome for can include high-speed framing cameras its postulated metastability and super- with high-explosive-driven argon flash conductivity. In the following sections, lamps, inductive pickup loops, and pulsed the known international research in this x-ray radiographic machines. The pressure area will be reviewed, the prognosis for obtained is not measured directly, but is metallic hydrogen will be discussed, poten- deduced from radiographic measurements and

tial military applications for the material indirect computations. Vereshchagin of the will be listed, and additional research Soviet Union says of the dynamic technique:

2 material onto an anvil of Carbonado, and

then loading the sample by means of a Carbonado plunger, as shown schematically

in Fig. 3. Pressures of several megabars W-Al’e’ona’orsare attainable over very tiny nonuniform areas. An alternate approach to the formation of metallic hydrogen has been proposed by

Hess of Germany. This method involves the

formation of atomic hydrogen by dissocia- tion via an electric discharge in a cryo- statted apparatus. The atomic form is - N-J{ maintained (without recombination to the /’4-\- \ -. molecular form) by means of high magnetic ‘Copper tube \\ fields. The magnetic fields would be used Stainless steelliner Vacuum to maintain spin alignment of the electron magnetic moments. Condensation of the atom-

ic form at temperatures below 1.2°K might Fig. 1. Cutaway vielw of experimental apparatus. lead to metallic hydrogen. Further inves- tigation of this method is being done at

NASA’s Lewis Research Center. The disadvantages of pulsed methods include the inability of saving the phases Reviews of the Soviet and US literature produced; moreover, the investigated phase on metallic hydrogen, to be presented in the transitions in many cases cannot take place within the time of existence of high pres- remainder of this section, show that most of sures. the reported work is of a theoretical The static technique is exemplified by nature. Despite the thorough theoretical the work of Vereshchagin et al. His understanding of the detailed behavior of a description of the technique is: single hydrogen atom, the ab initio deter- “Reaching such pressures by static mination of the characi eristics of a many- methods requires not only the forces of colossal presses, but especially new bodied substance (such as solid hydrogen) construction materials with outstanding from quantum theory is intractable. How- properties. Work is being conducted. .. on a press for investigating the problem ever> theoretical techn ques have success- of metallic hydrogen. The press is designed to produce a maximum force of 50 000 tons,” (See Fig. 2.) I “One of the most effective methods. .. is development of multistage chambers Steel holder with the proper choice of material for each stage. Carbonodo anvil “Detection of a new phase is also an Powdersomple important problem. The fixation of transition to the metallic state is possible on the basis of measurements of electrical conductivity and temperature dependence; detection of transition from the molecular lattice to the atomic can be done by measuring the proton resonance. ‘1Preswre The materials to which Vereshchagin refers include a form of man-made diamond -4- (Carbonado), a form of boron nitride (Borazon), tungsten carbide, and high- Fig, 3, Schematic of the anvils and qual- strength steels. The experimental procedure itative pressure distribution. involves placing a very thin layer of sample

3 Fig. 2. The 50 000-ton press at Krasnaya Pakhra. Only the portion above ground level is shown; the press’ foundation is located approximately five stories underground,

4 fully provided the framework to describe -pressure hydrogen. Metallic hydrogen, al- accurately the properties of some solids though considered to be important, is only and metals. The same techniques should a part of the large effort in a broad spec- also be credible for the prediction of a trum of high-pressure investigations. The metastable metallic solid hydrogen under IFVD staff with their special disciplines extremely high pressures. The high pres- could readily be used to exploit any sures are needed to order the hydrogen successes encountered by that portion of the nuclei in a regular lattice and to permit staff “directly engaged in metallic hydrogen the emergence of a band structure and cor- investigations. responding metallic behavior at room tem- The 50 000-ton press is the focal point peratures and even permit superconductivity at IFVO, because it would be the apparatus at much lower temperatures. One such the- ultimately used for the production of useful oretical technique is the free-electron quantities of metallic hydrogen, and perhaps version of the one-electron Hartree-Fock also ‘because it is the biggest press under method applied to the Born-Oppenheimer construction for high-pressure research. In approximation in which the electrons are May,1975 Vereshchagin told US visitors to assumed to move freely within an array of his installation that the completion date fixed nuclei. The assignment of approx- for the press would be June 1976. Indeed,

imate values, inferred from the macroscopic the visitors found it difficult to believe properties of other substances, to the ad- that the 50 000-totl press will be usable justable parameters in the approximate the- even by that date. The press was first oretical treatment is unsatisfactory. Such scheduled to be completed in 1972. a procedure has been used by some to pre- According to Vereshchagin, the theo- dict a room-temperature, atmospheric-pres- retical basis for their experimental effort

sure, stable, and superconducting metallic is in part the early theoretical work of hydrogen. An alternate description is I. M, Khalatnikov of the Landau Institute given by thermodynamic treatments which and Yu, M, Kagan of the Kurchatov Institute. indicate that metallic hydrogen will return It should be noted from Table II that to ordinary molecular solid hydrogen at Soviet theoretical efforts are not limited

ambient pressure and will exhibit no super- to these two institutes. Dynin at an un- conductive behavior above the sublimation known facility, Trubitsyn at the Schmidt point of solid molecular hydrogen.

B. Review of USSR Work TABLE I The greatest concentration of effort SITES OF SOVIET HIGH PRESSURE HYDROGEN WORK in the field of high-pressure research in

the USSR is at the Institute of High Pres- Institute of High Pres- Krasnaya Pakhra sure Physics sure Physics (IFVD) of the Academy of Lebedev Institute Moscow Sciences of the USSR at Krasnaya Pakhra Kurchatov Institute Moscow headed by Academician Leonid F. Vereshcha- (IAEh) gin. Other Soviet facilities are involved 0, Yu, Schmidt Geo- Moscow in investigations pertinent to metallic physical Institute hydrogen (but not necessarily limited to Institute of Metallurgy Moscow and Metal Physics such work) and are listed in Table I. Unknown Hydrodynamic USSR Only a portion of the total staff at the Institute IFVD are directly engaged in work on metal- Institute for Hydro- Akademgorodok lic hydrogen. Most of the 28 investigators dynamics Siberian SSR at IFVD listed in Table A-1 in the Appendix have published in areas other than high- TABLE II

RUSSIAN INVESTIGATIONS

PRINCIPAL SIZE OF PRESSURE WHEN WHERE INVESTIGATOR EFFORT RANGE METHOD USED SPECIES STUDIED

Present IFVD L. F. Vereshchagin Large 2-3 Mb Static Atomic & Krasnaya Pakhra UP to 5 Mb Molecular

1972 IAEh MOSCOW? F. V. Grigorev Smal 1 8 Mb Dynamic Molecular & S. B. Kormer Atomic

A. M. Prokhorov Smal 1 Theoretical Molecular

Present IAEh E. G. Brovman Sma11 Theoretical Atomic & Moscow Molecular

1966 0. Yu. Schmidt V. P. Trubitsyn small Theoretical Atomic Geophysical Institute Moscow

1971 Institute of Met. E. I. Estrin Smal 1 Theoretical Atomic and Metal Physics POscow

1972 Soviet Union (?) E. A. Dynin Smal 1 Theoretical Atomic

? Present Institute for V. M. Titov up to a Dynamic Molecular Hydrodynamics few Mb (Akademgorodok)

Geophysical Institute, and the Prokhorov lic hydrogen but does not and cannot direct- group at the Lebedev have also contributed ly verify any metallic property or the

to the theoretical aspects. existence of a metastable structure, It is More recently, the Institute for Hydro- perhaps because of this original claim that dynamics at Akademgorodok in the Siberian Vereshchagin feels comfortable in claiming

SSR is also reported to be working on hydro- to have made metallic hydrogen by the static

gen, employing a dynamic method, Thus far, method at IFVD. no publications on metallic hydrogen can be Notably absent from Table I and the attributed to this group, headed by V, M. more detailed listjng in Table II are the Titov. Soviet universities. It is known that some The first published claim for having high-pressure work is being done at Moscow made metallic hydrogen may be attributed to State University, but it is apparently not

the Kormer group at an unknown USSR hydro- related to metallic hydrogen. dynamic facility. Their dynamic technique In spite of the magnitude of effort and supports the postulated existence of metal- Vereshchagin’s recent claims, there is a

6 lack of unanimity even in the Soviet Union ity, most of it is done at pressures under on the success of the effort to produce 200 kb. Table III lists the US facilities. metastable metallic hydrogen. Estrin has The US high-pressure workers who have presented thermodynamic arguments which contributed to the hydrogen effort are list- predict that metastable metallic hydrogen ed in Table A-2 in the Appendix, A brief would melt at a lower temperature than review of US investigations more directly solid molecular hydrogen. Iordanskii et related to metallic hydrogen reduces the al. argue that the predicted metallic hydro- tabulation to the facilities and principal gen structure should be unstable due to un- investigators shown in Table IV. accounted-for small changes in the elec- The efforts at LLL include the unpub- tron-electron interaction. These points lished dynamic work of R. S. Hawke and co- can only be resolved experimentally. workers as well as several theoretical c. Review of US Work papers by M. Ross and coworkers. This is a In contrast to the Soviet centraliza- small effort. A few theoretical papers have tion of effort at the IFVD described in the been written at LASL dealing with the equa- previous section, the US effort in static tion of state of both hydrogen and deuterium. experimental high-pressure research is scat- Some experimental research using dynamic tered throughout a large number of US techniques has been done at LASLon deuterium. universities and institutions. Although the US high-pressure work is of excellent qual-

TABLE III

US STATIC HIGH-PRESSURE WORK UNDER 200 KBARS

Organizations Universities

Los Alamos Scientific Laboratory University of California (Los Angeles) Lawrence Livermore Laboratory University of California Sandia Corporation (San Diego) General Electric Corporation University of Illinois E. I. DuPont Co. Cornell University Bell Telephone Labs Penn State University National Bureau of Standards University of Chicago Carnegie Institution of Washington Brigham Young University (Geophysical Labs) M, I. T. (Lincoln Laboratory) United States Geological Survey University of Rochester Naval Ordnance Labs Princeton University Wright Patterson Air Force Base Iowa State University Lewis Research Center University of California (Berkeley) Rice University University of Maryland l/+BLt lV

US INVESTIGATIONS

PRINCIPAL SIZE OF PRESSURE WHEN WHERE INVESTIGATOR EFFORT RANGE METHOD USED SPECIES STUDIED

1973 Lawrence Livermore R. S. Hawke Smal 1 -3 Mb Dynamic Atomic Laboratory

Present Lawrence Livermore M. RoSS Very Small Theoretical Atomic Laboratory

Present LASL D. Liebenberg Sma11 20 kb Static Molecular

Present LASL G. Kerley Smal 1 Theoretical Atomic D. Liberman R. Mills

Present LASL R. Dick Smal 1 0,3 Mb Dynamic Molecular

Past LASL D. Janney Smal 1 9 Mb Dynamic Molecular

1968 to Cornel 1 A. Ruoff -3 Mb Static Molecular, Atomic Present (NSF) N. Ashcroft Smal 1 Theoretical Atomic Future

Present Watervliet L. V. Meisel Theoretical Molecular Arsenal J. F. COX Future D. M. Gray Sma11 -1 Mb Static Atomic

Present Lewis Research G. Brown Theoretical Molecular, Center (NAsA) Atomic

Future University of I. Spain Smal 1 -2 Mb Static At~mic Maryland (NASA)

Present N8S G. Piermarin Smal 1 >-.75 Mb Static No Hydrogen Work

Present Colorado State K. D. Etters Few Theoretical Atomic University (NAsA) A. Anderson LASL)

1962 Westinghouse W. J. Carr, Jr. Few Theoretical Research Labs

1971 University of F. E. Harris Few Theoretical Molecular, Utah - Atomic

8 Cornell University and Watervliet ful of people as shown in Table A-3 in the Arsenal have parallel programs for hydrogen Appendix. This work is of good quality and work insofar as both facilities are con- has been adopted as a basis for further structing presses and are simultaneously research by both Russian and US investiga- publishing theoretical papers. The presses tors. The concept of forming and stabiliz- would be useful for research but would not ing atomic hydrogen by a dissociating elec- be capable of producing large quantities of tric discharge was initiated by R. Hess in metallic hydrogen and would not achieve the Germany and has been adopted for further megabar range of pressure in the near development in the US. Vereshchagin has future. been quoted as relying on the theoretical

Some of the impetus for the research work of T. Schneider of Switzerland for on metallic hydrogen is due to the theo- furthering the Soviet investigations. The retical work of N. Ashcroft at Cornell in theoretical publications of Caron of Canada which the possibility of room-temperature and Ostgaard of Norway are also well regard- superconductivity was reported based on the ed. These investigators and their affil-

Bardeen, Cooper, and Schrieffer (BCS) theory iations are listed in Table V. The Japanese of superconductivity. The early work of A. high-pressure work is predominantly exper-

Ruoff at Cornell was funded by ARPA, but imental and is the nearest potential compet- his funding is now from NASA and NSF as is itor to the Soviet effort. the funding for the more recent theoretical N, Kawaii of Japan has built a split- papers from Cornell. sphere apparatus, in which the simplest Carr published theoretical papers in single-stage version consists of segments 1962 from the Westinghouse Research Labor- of spheres with truncated inner faces assem- atory, but, apart from Cornel’ , the more bled together with small spaces between recent publications have been from the on- them, The front faces that form the anvils going work of R. Etters at Co’ orado State enclose the sample to be compressed. Move- University and Harris and his colleagues at ment is accomplished by surrounding the out- the University of Utah as wel as LASL and side of the sphere with a deformable mem-

LLL. brane and immersing the sphere in a fluid Although no hydrogen work has as yet for pressing in a I-hydrostatic chamber. By been done at the National Bureau of Stand- increasing the stages, and thus increasing ards (NBS), the highest pressure presently the external surface area compared to the atta nable in the US by static techniques internal surface area of the sphere, pres- (0.7! Mb) would be available there. sure multiplication factors in excess of

The NASA-sponsored work at the Lewis 103 may be readily achieved, A three-stage Research Center in Cleveland and at the press is being developed at the Osaka University of Maryland are of interest, the University. Professor Kawaii has 10 to 15 former because of the unique approach to the graduate students investigating various formation of atomic hydrogen with subsequent aspects of high-pressure physics. According separation, The University of Maryland high- to Kawaii, the volume in the center of the -pressure research directed by I. I. Spain split-sphere apparatus is much greater than plans to use the split-sphere press concept that planned for the 50 000-ton press in the for attaining pressures in the megabar Soviet Union and is still capable of reach- range. This technique will be described in ing pressures of 1 to 2 Mbars. The Univer- the review of Japanese work. sity of Maryland’s apparatus is an outgrowth D. Review of Work in Other Countries of the Kawaii split-sphere press, an out- The work done on metallic hydrogen in come of I. 1. Spain’s year in Japan with both Europe and Canada involves but a hand- Kawai i .

9 TABLE V

INVESTIGATIONS BY OTHER COUNTRIES

PRINCIPAL SIZE OF PRESSURE WHEN WHERE INVESTIGATOR EFFORT RANGE METHOD USED SPECIES STUDIED

1969 to IBM Zurich T. Schneider Smal1 Theoretical Atomic Present Switzerland

Present Tokyo University S. Minomura Sma11 1-2 Mb Static No Hydrogen Osaka University N. Kawaii 15 People Work Yet Okayama University T. Ito Smal 1 Japan

1971 Stuttgart R. Hess Few Low Static Atomic I Germany (-100 atm)

1973 University of E. Ostgaard Few Theoretical Metallic Trondheim Norway

Present Canada L. G. Caron Few Theoretical Atomic

S. Min.omura of Japan has studied in sures. Experimental high-pressure shock-

the US with Drickamer at the University of wave data for molecular hydrogen are inter- Illinois prior to establishing his own high- preted as indicating the formation of the -pressure facility. metallic form. T. Ito, a member of the Japanese Acad- Its formation is suggested in a gen- emy of Sciences, is assumed to have been in eral way by the prediction and observation the high-pressure field for some time. of metallic phases of other materials. One example is metallic carbon, also prepared III. THE PROGNOSIS by Vereshchagin’s group using the static

The announced formation of metallic. pressure technique. The metal was pre-

hydrogen by Vereshchagin and coworkers at pared at a pressure of about 1 Mbar. On the IFVO will increase interest in this lowering the pressure somewhat below the material and accelerate studies of its prep- dielectric/metallic transition point, the

aration and properties. The independent metal was metastable and transformed back

verification of its preparation is of pri- to diamond when heated at the reduced

mary importance. Other evidence supports pressure. Upon raising the temperature the existence of metallic hydrogen; on further, it was possible to cross the ret- theoretical grounds, it has been predicted rograde diamond-to-metal pressure-tem- to exist under conditions of megabar pres- perature phase boundary to again form the

10 metal. This behavior is similar to that the corresponding stable phase; the melting observed for silicon and germanium, which and boiling points of metallic hydrogen have also been prepared in metallic form at should thus be lower than 14 and 20”K high pressure, and to that of the grey-to- respectively. The preparation and proper- white tin transformation (common white tin ties of metallic deuterium should be sim- metal is metastable below 18°C). Other ilar, but more favorable (molecular deute- substances that have been prepared in metal- rium has melting and boiling points of 18.6 lic form at high pressures are compounds and 23,6°K respectively). that are electronically and crystallograph- Metallic hydrogen may melt to form a ically similar to tin and germanium, and liquid metal (now assumed to give Jupiter include ZnS, ZnSe, ZnTe, CdSe, CdTe, Al As, and outer planets a magnetic field) and InP, InAs, InSb (metastable at -25”C), vaporize to form atoms rather than mol- GaAs, and GaSb, together with the dissimilar ecules, particularly if the atomic vapor substances S, I, Se, Si02, NaCl, A1203, TaN, pressure (and hence the atomic-to-molecular The latter two are both low- recombination rate) is assumed to be ex- and ‘a2s3” temperature superconductors and are metasta- tremely low, In this case, metallic and ble under ambient conditions. molecular hydrogen might be viewed as two The preparation of metallic hydrogen different substances (e.g., oxygen, 02, and in metastable form is of vital interest, at ozone, 03), and metallic hydrogen might ex- least at low temperatures and ambient pres- hibit considerable stability. Furthermore, sure. Unfortunately, no evidence exists several theoretical approaches consider the that it is metastable at ambient pressure, metal to be similar to lithium and other nor have any stabilizers been reported. alkali metals, and the Oebye temperature Hopefully, substances such as lithium might has been calculated to be well above 1000”K. be added to stabilize the metallic form; LiF Vereshchagin’s reported observation of an has been suggested as a stabilizer, Some instability at a few hundred kilobars at metastability was reported by Vereshchagin 4°K and at somewhat higher pressures at et al, namely, that metallic hydrogen was 20”K indicates that this type of stability metastable to a few tenths of a megabar and is not obtained. A quench under pressure to a temperature of 20”K under pressure. to about l°K has not been reported and Even a careful search for a stabilizer may should be tried. Certainly, confirmation not be successful, but at least a cursory of the instability merits consideration. search will be made by present investigators. Iv, POTENTIAL MILITARY UTILITY Another critical area is the determina- For the purpose of discussing the tion of the physical and chemical properties potential military utility of metallic of metallic hydrogen. In particular, there hydrogen, and depending upon the particular has been considerable interest recently in applications, at least some of the following the application of metallic hydrogen as a assumptions will be made regarding the “room-temperature” superconductor, The material : stabilization of the metal at room tempera- 1. It will be metastable under all ture is clearly less probable than that at natural environmental conditions.

low temperature. Suggestive of the problems 2. It will be superconducting at are the melting and boiling points that temperatures at least as high as might be expected for the metastable form. the boiling point of nitrogen On the basis of phase studies and thermo- (77”K). dynamic considerations, metastable phases

have lower melting and boiling points than 3. It will be chemically compatible controlled only in those cases where the with at least some containment material is finely divided (as is the case materials. in most conventional high explosives such 4. The release of atomic-molecular as ROX), then applications could include transition energy (about 400 kJ rocket motor fuel for propulsion or pulsed

per gram-mole) can be obtained on power (e.g., MHO) sources. If the reaction demand. is totally controllable, additional applica- 5. It can be produced economically in tions may include heat sources for compact

quantity. power supplies (fuel cells, etc.), and A. Compact Energy Storage propellant for nuclear-powered propulsion It has been estimated that the energy units. required to achieve the molecular-atomic The application of metallic hydrogen transition in hydrogen is about 400 kJ/ to conventional bombs and shells is attrac- gram-mole. This energy, provided from an tive in terms of available firepower. Since external source during formation of the the density of metallic hydrogen is post- metallic form, would be stored in the atomic ulated to be about 1 g/cm3, a shell designed lattice and be available through initiation to contain 10 kg of TNT would contain 6.3 of the reaction 2H + H2. A weight-basis kg of metallic hydrogen whose energy yield comparison of this energy release with that would be 27 times that of the TNT. of more familiar reactions is given in Table B. High-Temperature Superconductors VI; the transition energy is about 40 times Estimates of the critical temperature that of TNT. (Tc) of the postulated superconducting If the transition energy release rate metallic hydrogen range from <14°K to room is not controllable once the reaction is temperature (about 300”K). At the present initiated, applications may be limited to time, superconductors have little or no explosive devices such as conventional direct military applications because of the bombs and shells. If the reaction can be elaborate cryogenic equipment required to maintain the very low temperatures necessary for superconductivity. If the optimistic

TABLE VI

ENERGY RELEASE

Reaction Approx. Energy (J/g)

Thermonuclear Fusion 2.8 X 101] (O-T)

Fission of Uranium 8 X 1010

2H + H2 2 x 105

Hydrogen Combustion 1.2 x 105 2H2 + 02 + 2H20

TNT Detonation 4.6 X 103

12 estimates for T ~ are more nearly correct, in the US from Megadiamond Corp. of Provo, several immediate applications may be found. Utah. This material might be used to Nearly every current-carrying element duplicate Vereshchagin’s anvils. in aircraft and missiles could be improved It is clear now that the construction through substitution of metallic hydrogen of the huge 50 000-ton press at Krasnaya for the presently-used copper, silver or Pakhra was not undertaken just to verify aluminum, on the basis of weight savings the existence of metallic hydrogen. How- alone. However, the future for military use ever, the press will be a research tool with of superconductors probably lies in advanced unique capability to produce super-hard weapons of the beam type (lasers, neutral- materials in quantity. In addition, it will or charged-particle). These weapons will have the capability to provide relatively use huge pulses of electrical power; the large samples of materials in metastable or energy generation, storage, and conditioning metallic states -- samples large enough to equipment will have to be light, rugged, and allow good determination of their physical efficient. Magnetic energy storage and properties, There are larger presses al- field devices, e.g., inductive stores and ready in existence in the Soviet Union and magnets, are logical applications of super- in the US (about 70 000 tons capacity). conductors, but their practicability is The distinguishing feature of Vereshchagin’s presently limited by the necessary cryogenic press is that the design of the press is equipment. uniquely suited to research purposes, rather Although it is not of immediate mil- than to the production of large metal stamp- itary significance, one of the major present ings, forgings, or extrusions. applications for superconductors is in elec- There are several major questions that trical power transmission lines. The goal must be addressed before the value of metal- of this work is the development of nearly lic hydrogen can be assessed. These ques- lossless transmission lines for high-cur- tions are posed and discussed in the follow- rent, high-voltage, DC power transfer. ing: c. Laser Fusion Q: IS the Postulated metastability Present laser fusion research is real ? directed toward laser-induced implosion of Is the postulated superconduc- small pellets of a liquid deuterium/tritium tivity real? mixture. Substitution of the metallic form Vereshchagin’s results only indicated a would allow higher densities, and hence transition to the conductive (and inferred higher energy yields, to be obtained. metallic) state, and an unknown degree of metastability with respect to pressure re- v. NECESSARY ADDITIONAL RESEARCH lease at very low temperatures. All other Independent confirmation of Vereshcha- regimes in which metastability is important, gin’s announced experimental result should i.e., low temperature and low pressure, room be undertaken using his type of apparatus. temperature and high pressure, room temper- His data indicate a total load on the Car- ature and low pressure, remain to be inves- bonado anvils of only 50 kg -- a load that tigated. is easily obtainable with routine laboratory A complete and detailed pressure-vol- equipment. High pressures were achieved by ume-temperature map is required for hydro- virtue of the extremely small contact area gen, Estimates have been made of the effort of the anvils (approximately 0.1 mm diam- required to obtain such a map. With the eter). Carbonado-type material is available static technique, and pressures up to about

100 kbars, three to five people would re-

quire about 5 yr. With the dynamic technique,

13 a similar effort would be necessary to work. These publications are included in extend the pressure range up to about 1 the following lists. Mbar.

Q: What is the feasibility and A. Soviet Publications - Specific on Metal- necessity of producing atomic lic Hydrogen hydrogen? 1. Trubitsyn, V. P., “Equation of State of Solid Hydrogen,” Soviet Physics - Solid Current experimental approaches start State ~ (11), 2708-2714 (1966) Translat- with the molecular form of hydrogen and ed from Fizika Tverdogo Tela ~ (11), 3363-3371 (1965). attempt to achieve the metallic form through

direct application of pressure. The metal- 2. Trubitsyn, V. P., “Van Der Waal~ Forces at High Pressures,” Soviet Physics - lic form is an atomic, not molecular, form. Solid State 7, 11, 2779-2780 (1966) It has been suggested that one should start Translated from Fizika Tverdogo Tela ~, (11), 3443-3445 (1965). with the atomic (i.e., dissociated) form in

order to get the metal. However, the strong 3. Trubitsyn, V. P., “Phase Transition in a Hydrogen Crystal,” Soviet Physics - tendency for atomic hydrogen to recombine Solid State 8 (3), 688-690 (1966) Trans- into the molecular form may preclude this lated from F~zika Tverdogo Tela A (3), 862-865 (1966). approach. Hess’ suggestion involving strong external magnetic fields may offer a way out 4. Bogdankevich, O. V., Rukhadze, A. A., “Possibility of Producing High Pressure of this difficulty; it may even make the in a Solid by Means of a Strong-Current application of high pressures unnecessary. Electron Beam,” ZhETF Pis. Red. ~ (9), 517-519 (1971). The behavior of free atomic hydrogen in the

presence of the molecular form at low tem- 5, Estrin, E. I., “Temperature Stability of the Metallic Modification of Hydro- peratures and pressures is not well known gen,” ZhETF Pis. Red.13— (12), 719-720 and should be vigorously investigated. (1971)

6. 8rovman, E. G., Kagan, Y., Kholas, A., ACKNOWLEDGMENTS “Structure of Metallic Hydrogen at Zero Pressure,” Zh. Eksp. Teor. F~z. m, The authors wish to thank the many 2429-2458 (1971), LASL personnel and consultants who have 7. Brovman, E. G., Kagan, Yu., Kholas, A., provided timely information and suggestions “Properties of Metallic Hydrogen Under for this report. Particular thanks are Pressure,” Zh. Eksp. Teor. Fiz. H_, 1492-1501 (1972). extended to T. R. Neal and D. Liebenber9 for their review of the manuscript and for 8. Vereshchagin, L. F. and Arkhipov R. G., “Production of Metallic Hydrogen,” their valuable suggestions. In addition, Priroda, (3), 9-12 (1972), Translated the textual material provided by the JPRS 56130 (1972).

contributors is gratefully acknowledged. 9. Dynin, E. A., “Transition of Hydrogen to the Metallic State,” Soviet Physics - Solid State 13 (8), 2488-89 (1972), REFERENCE Translated f=m Fizika Tverdogo Tela ~ 1. R. S. Hawke, D. E. Duerre, J. G. Huebel, (8), 2488-89 (1972). H. Klapper, D. J. Steinberg, and R. N. Keeler, “Method of Isentropically Com- 10, Grigorev, F, V., Kormer, S. B. Mikhail- pressing Materials to Several Megabars,” ova, O. L., Tolochko, A. P., Urlin, V. J. Appl. Phys. ~, No. 6, 2735 (1972). o “Experimental Determination of the C;;pressibility of Hydrogen at Densities 0.5 - 2g/cm3. Metal ization of Hydro- BIBLIOGRAPHY gen,” ZhETF pis. Red. _16 (5), 286-290 (1972). Numerous publications have been found

in the open literature on the subject of 11. Anisimov, S. I., “Transition of Hydrogen into the Metallic State in a Compression metallic hydrogen and related high-pressure Wave Induced by a Laser Pulse,” ZhETF Pis. Red. 16 (10), 570-572 (1972).

14 12. Iordanskii, S. V., Lokutsievskii O. V., 7. Popova, S. V., Fornicheva, L. N., Pal’- Vul, E. B,, Sidorovich, L. A., Finkel ’- nikov, N. I., “Superconductivity of Nb- shtein, A. M., “Instability of Metallic Ru Alloys Synthesized at High Pres- Hydrogen Structure to Small Changes in sure,” ZhETF Pis. Red. ~ (10), 648-650 the Allowance for the Electron-Electron (1974). Interaction,” ZhEFT Pis. Red. —17 (9), 530-534 (1973). 8. Vereshchagin, L. F., Yakovlev, E. N. Vinogradov, B. V., and Sakun, V. P., 13. Askaryan, G. A., Namiot, V. A., Rabino- “Dielectric-to-Metal Transitions under vich, M. S., “Supercompression of Matter Pressures P-1 Mb.,” Proceedings of the by Reaction Pressure to Obtain Micro- Int’1 Conference on High Pressures, critical Masses of Fissioning Matter, Kyoto, Japan (1974). to Obtain Ultrastrong Magnetic Fields, and to Accelerate Particles,” ZhETF 9. Vereshchagin, L. F., Yakovlev, E. N., Pis. Red. ~ (10), 597-600 (1973). Vinogradov, B. V., Stepanov, G. N., Bibaev, K. Kh., Alaeva, T. I., Sakun, P., “Megabar Pressure between An- 14. Brovman, E. G., Kagan, Yu., Kholas, A., v. vils,” High Temperature-High Pressures Pushkarev, V. V,, “Role of Electron- g, 499-504 (1974). Electron Interaction in the Formation of a Metastable State of Metallic Hydro- gen ,“ ZhETF Pis. Red. ~ (4), 269-273 10. Vereshchagin, L. F., Yakovlev, E. N., (1973). Vinogradov, B. V., Sakun, V. P., Ste- panov, G. N., “Transition of Diamond into the Metallic State,” High Tem- 15. Vereshchagin, L. F., Yakovlev, E. N., perature-High Pressures 6_, 505-508 Timofeev, Yu. A., “Possibility of (1974). Transition of Hydrogen into the Metal- lic State,” ZhETF Pis. Red, _21 (3), c, 190-193 (1975). US Publications 1. Wigner, E. and Huntington, H. 8., “On B. Soviet Publications - High-Pressure the Possibility of a Metallic Modifica- tion of Hydrogen,” Journal of Chem. Related Work Physics ~, 764-770 (1935). 1. Vereshchagin, L. F., Yakovlev, E. N., Varfolomeeva, T. D,, Slesarev, V, N,, 2, Alder, B, J. and Christian, R. H., Shterenberg, L. E., “Synthesis of Dia- “Destruction of Diatomic Bonds by Pres- monds of the ‘Carbonado’ Type,” Doklad, Akad. Nauk SSR 185 (3), 555-556 [1969).

2. Vereshchagin, L. F., Semerchan, A. A,, 3. Carr, W. J., Jr., “Ground-State Energy Modenov, V. P., Bocharova, T. T., Dmit- of Metallic Hydrogen I,” Phys. Review riev, M. E., “Synthetic Diamond - A 128 (l), 120-125 (1962). Material for High-Pressure (Megabar) Chambers,” Doklady Akademii Nauk SSR 4, Carr, W. J., Jr., “Many Electron Per- ~ (3), 593-594 (1970). turbation Theory for Nonmetallic Low- Density System,” Phys. Review 131 (5), 3. Vereshchagin, L. F., Yakovlev, E. N., 1947-1952 (1963). Stepanov, G. N., Vinogradov, B, V,, “Possible Transition of Diamond into 5. Raich, J. C., “Discussions of the Destruction of Diatomic Bonds in Mol- the Metallic State,” ZhETF Pis. Red. —16 (7), 382-383 (1972). ecular Crystals by Pressure,” J. Chem. Physics —45 (7), 2673-2674 (1966). 4. Vereshchagin, L. F., Yakovlev, E, N., Vinogradov, B. V., Sakun, V. P,, Ste- 6. Ashcroft, N, W., “Metallic Hydrogen: panov, G. N., “Concerning the Transi- A High Temperature Superconductor?” tion of Diamond into the Metallic Phys. Review Letters —21 (26), 1748- State,” ZhETF Pis. Red. ~ (8), 422-424 1749 (1968). (1973). 7. Kass, R, S. and Williams, W. L., 5. Vereshchagin, L. F., Yakovlev, E. N., “Quenching of Metastable Hydrogen by Vinogradov, B. V., Sakun, V. P., Ste- Helium,” Phys. Rev. Letters —27 (8), panov, G. N., “Transition of Si02 to 473-474 (1971). the Conducting State,” ZhETF Pis. Red. ~ (7), 472-474 (1974). 8. Gilman, J. J,, “Lithium Dihydrogen Fluoride - An Approach to Metallic 6. Vereshchagin, L. F., Yakovlev, E. N., Hydrogen,” Phys, Review Letters —26 Vinogradov, B. B., Sakun, V. P., (10), 546-548 (1971). “Transitions of A1203, NaCl and S into the Conducting State,” ZhETF Pis. Red. —20 (8), 540-544 (1974).

15 9, Harris, F. E. and Monkhorst, J. J., 20. Meisel, L. V. and Cox, J. F., “Inter- “’Exact’ Hartree-Fock Calculations for molecular Forces and Equation of State Atomic-Hydrogen Crystal,” Solid State for $glid Molecular Hz, Dz, 3He, “He Communications ~, 1449-1453 (1971). and Ne,” Phys. Review —11 (4), 1762- 1767 (1975). 100 Neece, G. A., Rogers, F. J., Hoover, M, G., “Thermodynamic Properties of 21. Van Thiel, M., Herd, L., Gust, W., Compressed Solid Hydrogen,” Journal of Mitchell, A., D’Addario, M., Boutwell, Computer Physics 7_, 621-636 (1971). K Wilbarger, E,, Barrett, B., “Shock C~~pression of Deuterium to 900 Kbar,” 11. Kerley, G. I., “A Theoretical Equation Lawrence Livermore Laboratory Report of State for Deuterium,” Los Alamos UCRL-75446 (February 1974). Scientific Laboratory report LA-4776 (January 1972). 22. Hammerberg, J. E., “Structural Proper- ties of Metallic Hydrogen”, Cornell 12. Salpeter, E. E., “Evaporation of Cold University report 2134 (1974). Metallic Hydrogen,” Phys. Rev. Letters —28 (9), 560-562 (1972). 23. Anderson, A. B., Raich, J. C., and Etters, R. D., “Self-Consistent Phonon Calculations and Equations of State 13. Chapline, G. F., Jr., “Metal-Insulator of Solid Hydrogen and Deuterium,” to Transition in Solid Hydrogen,” Phys, be published. Rev. 8 ~ (6), 2067-2070 (1972).

D. Other Foreiqn Publications on Metallic 14. Ruoff, A. L., “Penultimate Static Pres- sure Containment Considerations and Hydrogen Possible Applications to Metallic 1. Kronig, R., Deboer, J., Korringa, J., Hydrogen Preparation,” Advannes in Cry- “On the Internal Constitution of the ogenic Engineering —18, 435-4$0 (1973). Earth,” Physics 12 (5), 245-256 (1946).

15. Spain, I. I., Ishizaki, K., Marchello, 2, March, N. H., “On Metallic Hydrogen,” J. M., Paauwe, J., “Prospects for Physics ~, 311-314 (1956). Obtaining Metallic Hydrogen with Spher- ical Presses,” Advances in Cryogenic 3. Bellemans, A. and DeLeener, M., Engineering —18, 441-446 (1973). “Ground-State Energy of an Electron Gas in a Lattice of Positive Point Charges,” 16. Hoover, W. G., Keeler, R. N., Van Phys. Rev. Letters ~ (11), 603-604 Thiel, M., Herd, B. L., Hawke, R. S., (1961). Olness, R. J., Ross, M., Rogers, F. J., Bender, C. F., “High-Density Hydrogen 4. Calais, J. C., “Different Bands for Research,” Advances in Cryogenic Different Spins III. Solid Atomic Engineering ~, 447-451 (1973). Hydrogen,” Arkiv Fysik —29 (18), 255- 273 (1965). 17. Van Thiel, M., Herd, B. L., and Bout- well, K,, “Shock Waves in Hydrogen 5. Schneider, T., “Metallic Hydrogen I.” Isotopes and Their High Pressure Equa- Helv, Phys. Acts ~, 957-989 (1969). tion of State,” Lawrence Livermore Laboratory Report UCRL-75727 (October 6, Schneider, T., Metallic Hydrogen,” Solid 1974), presented at the 4th Int’1 State Communications ~, 875-876 (1969). Conference on High Pressure, Kyoto, Japan (November 25-29, 1974). 7. Schneider, T. and Stoll, E., “Metallic Hydrogen II. High Temperature Super- 18. Ross, M., “A Theoretical Analysis of conductivity,” Physics —55, 702-710 the Shock Compression Experiments of (1971). Liquid Hydrogen Isotopes and A Pre- diction of Their Metallic Transition,” 8, Ostgaard, E., “Solid Hydrogen. Trans- Journal of Chemical Physics ~ (9), ition into a Metallic Phase at High 3634-3644 (1974). Densities,” Physics Letters 45A (5), 371-372 (1973). 19. Ross, M., Ree, F, H., Keeler, R. N,, “A Summary of the Recent Lawrence 9. Hess, R., “Atomic Hydrogen Stabilization Livermore Laboratory (LLL) Work on the by High Magnetic Fields and Low Tem- Equation of State of Dense Molecular peratures,” Advances in Cryogenic Engi- Hydrogen,” Lawrence Livermore Labor- neering —18, 427-434 (1973). atory Report UCRL-75761 (February 1975), Dresented at the 4th Int’1 10. Caron, L, G., “Low-Temperature Ther- Conference on High Pressure, Kyoto, mostatic of Face-Centered-Cubic Metal- Japan (November 25-29, 1974). lic Hydrogen,” Physical Review 8 ~ (12), 5025-5038 (1974).

16 110 stoll, E., Meier, p. F., Schneider> TOS 7. “Quest for Metallic Hydrogen,” New “Metallic Hydrogen IV. Equation of Scientist, 644 (June 1971). State,” 11 Nuovo Cimento 23 (l), 90-101 (1974), 8. “Planet Jupiter Consists of Liquid Hydrogen,” Aviation Week and Space Technology, 40-41 (September 1974). E, General Metallic Hydrogen - ReliAted Publications 9. “Atomic Hydrogen Fuels Studied,” Avia- tion Week and Space Technology (Nov- 10 Arkhipov, R. G., Itskevich, E. S., ember 1974). Likhter, A. I., Popova, S. V., “Solids at High Pressures,” Priroda 2_, 3-13 (1967). 10. “Review of Academy of Sciences’ Work in 1974,” Sotsial isticheskaya Indus- 2, Khalatnikov, I. M., “Problems of Metal- triya (54), 1-2 (March 1975). lic Hydrogen,” Priroda ~, 8-11 (1971). 11. “New High Pressure Mechanical Press,” 3, Vereshchagin, L. and Khalatnikov, E., Moskovskaya Pravda, (99), 3 (April “Metal from Hydrogen: Fantasy or 1975). Reality?” Nedelia (21), 585 (1971). 12. Vereshchagin, L. F., “SuP:r-Powerful 4. Metz, W. D., “Metallic Hydrogen: Sim- Press for Creating Metalllc -Hydrogen,” ulating Jupiter in the Laboratory,” Trud (178), 4 (JuIY 1975). Science ~, 398-399 (1973). 13. Wolfe, J. H., “Jupiter,” Scientific American ~ {3), 119-126 (1975). 5. “soviet and US Groups Seek Hydrogen’s Metallic Phase,” Physics Today, 17-20 (March 1973).

6. “The Continuing Search for Metallic Hydrogen,” Industrial Research, 25 (1973).

APPENDIX

HIGH-PRESSURE RESEARCHERS

Table A-1 contains a list of known work of some has been confined to molecular

high pressure research personnel in the hydrogen. Soviet Union. Most of these people are Table A-3 is a list of persons engaged

directly concerned with metallic hydrogen, in high-pressure work in other countries. Table A-2 is a list of personnel engag- The Japanese have not been concerned with

ed in similar work within the US. Not all hydrogen, but they have the capability of of the US personnel listed have worked doing high-pressure hydrogen work. specifically on metallic hydrogen -- the

— TABLE A-1 Location Unknown

F, V. Grigorev S. B. Kormer KNOWN SOVIET HIGH PRESSURE RESEARCHERS O. L. Mikhailova A. P, Tolochko V. D, Urlin E. A. Oynin

Institute of High Pressure Physics ------

L. F. Vereshchagin N. Kuzin TABLE A-2 E. N. Yakovlev V. A, Stepanov Y. A. Timofeev T. D. Vartolomeeva G. N. Stepanov V. N. Slesarey US HIGH-PRESSURE RESEARCHERS V. P. Sakun L. E. Shterenberg B. V. Vinogradov S. M. Stishov A. A. Semerchan J. S. Konyayev Cornell University V. P. Modenov N. S. Fateeva T. T. Bocharova F, F. Voronov J, A, Krumhansl N. W. Ashcroft S. V. Popova V. V. Evdekimova E. L. Pollock A. L. Ruoff N. I. Pal ’nikov S. S. Kabalkina T. A. Bruce E. E. Salpeter L. N. Fomicheva G. E. Itskevich G. V, Chester D. Straus V. Badanov V. V. Kechin Yu. Sadkov D. A, Alichunov

Lawrence Livermore Laboratory

Institute of Atomic Energy imeni Kurchatov W. G. Hoover C. F. Bender R, N. Keeler D. Boutwell E. G. Brovman A. Kholas M. Van Thiel M. ROSS Yu. M. Kagan V. V. Pushkarev B. L, Herd F. H. Ree R, S. Hawke G. F. Chapline, Jr, R, J. Olness J. G, Huebel F, J. Rogers Institute of Physics imeni Lebedev

G. A. Askaryan V. A. Namiot M. S. Rabinovich M. A. Markov University of Utah A. M. Prokhorov O. N. Krokhin O. V. Bogdankevich A. A. Rukhadze David E, Ramaker Lalit Kumar Frank E, Harris J. J. Monkhorst

Institute for Theoretical Physics imeni Landau Los Alamos Scientific Laboratory I. M. Khalatnikov S. I. Anisimov S. V. Iordanski O. V, Lokutsievskii D. Liebenberg E. Kmetko E. B. Vul L. A. Sidorovich D, Liberman A. Anderson A. M. Finkel’shtein G. I. Kerley M. Krupka D. Janney R. Mills T. Neal C. M. Fowler R, Dick Geophysical Institute imeni Schmidt

V. P. Trubitsyn V. Zharkov A. Makal kin NASA Lewis Research Center

G. V. Brown

Institute of Metallurgy and Metal Physics

E. I. Estrin University of Michigan

R. S. Kass W. L. Williams

Institute of Hydrodynamics (Akademgorodok)

V. M. Titov University of Maryland

I. I. Spain J. M. Marchello J. Paauwe

lB Purdue University GERMANY:

J. D. Raich (Presently at Colorado State University) Stuttgart

R. Hess

Iowa State University

C. A. Swenson CANAOA:

University of Sherbrooke

US Military Academy,.West Point L. G. Caron

W. Streett

------NORWAY:

TABLE A-3 University of Trondheim

E. Ostgaard KNOWN HIGH-PRESSURE RESEARCHERS OF OTHER COUNTRIES

JAPAN : SWITZERLAND:

Osaka University IBM Zurich

N. Kawaii A. Nishiyama T. Schneider E. Stoll S. Mochizuki A. Onodera P. F. Meier H. Fujita M. Togaya S. Endo

University of Zurich

Tokyo University H, Beck

S. Minomura (FNU) Akimoto

Okayama University

T. Ito

*US @OVERNMENT PRINTING OFFICE. 1978-677.343/60