UNLV Theses, Dissertations, Professional Papers, and Capstones 12-15-2018 Studies of Inner-Shell Chemistry of Mercury Based Compounds at Extreme Conditions Sarah Schyck Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Physics Commons Repository Citation Schyck, Sarah, "Studies of Inner-Shell Chemistry of Mercury Based Compounds at Extreme Conditions" (2018). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3453. http://dx.doi.org/10.34917/14279172 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. 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STUDIES OF INNER-SHELL CHEMISTRY OF MERCURY BASED COMPOUNDS UNDER EXTREME CONDITIONS By Sarah Schyck Bachelor of Science in Physics University of Georgia 2015 A thesis submitted in partial fulfillment of the requirements for the Master of Science - Physics Department of Physics and Astronomy College of Sciences The Graduate College University of Nevada, Las Vegas December 2018 Thesis Approval The Graduate College The University of Nevada, Las Vegas November 19, 2018 This thesis prepared by Sarah Schyck entitled Studies of Inner-Shell Chemistry of Mercury Based Compounds under Extreme Conditions is approved in partial fulfillment of the requirements for the degree of Master of Science - Physics Department of Physics and Astronomy Michael Pravica, Ph. D. Kathryn Hausbeck Korgan, Ph.D. Examination Committee Chair Graduate College Interim Dean Eunja Kim, Ph. D. Examination Committee Member Stephen Lepp, Ph. D. Examination Committee Member David Hatchett, Ph. D. Graduate College Faculty Representative ii ABSTRACT STUDIES OF INNER-SHELL CHEMISTRY OF MERCURY BASED COMPOUNDS UNDER EXTREME CONDITIONS by Sarah Schyck Prof. Michael Pravica, Defense Committee Chair University of Nevada, Las Vegas It has been theoretically predicted that when mercury difluoride (HgF2) is pressurized to above 50 GPa in the presence of molecular fluorine, it will most likely transform into mercury tetrafluoride (HgF4), thus mercury will behave as a transition element at high pressure. However, there is no experimental evidence verifying this prediction yet. To begin with, the crystalline properties of pure HgF2 at high pressure were not experimentally established. In this thesis, the high pressure structural properties of HgF2 are investigated by means of synchrotron X-ray powder diffraction. Our results reveal that the predicted, ambient cubic structure of HgF2 with the space group Fm- 3m, can be obtained via a high-pressure ramp purification process using powdered HgF2 mixed with crystalline XeF2 which serves as our molecular fluorine source. The structural transformation of purified HgF2 is observed above 2.5 GPa, and by using first-principle calculations, two candidate structures with space groups Pnma and Pnam are proposed which persist up to 63 GPa. Furthermore, studies of HgF2 in the presence of F2 produced by the X-ray induced decomposition of XeF2 up to 70 GPa are reviewed. The obtained results provide more insights into the high- pressure behavior of mercury-fluorine compounds and will benefit further experimental investigation of high pressure induced synthesis of HgF4. iii ACKNOWLEDGMENTS I want to express my gratitude to my supervisor for his professional guidance during this thesis project. Specifically, thank you Professor Michael Pravica for providing me the opportunity to complete this master’s thesis in his research group. I would also like to thank Dr. Eunja Kim for her ideas and discussions during these years. I am grateful to the other official committee members of this thesis, Professor Stephen Lepp and Professor David Hatchett, for their encouraging comments and professional review. I would like to express my appreciation to all my co-authors for their contributions to these studies. Particularly, I want to thank Dr. Egor Evlyukhin for his endless help in analyses and support during my thesis project. I want to acknowledge the staff of Argonne National Laboratories, HPCAT Sector 16 and the Canadian Light Source for their help during this project. For financial support, I gratefully acknowledge support from the Department of Energy National Nuclear Security Administration (DOE-NNSA) under Award Number DE-NA0002912. I also acknowledge support from the DOE Cooperative Agreement No. DE-FC08-01NV14049 with the University of Nevada, Las Vegas. I am grateful to my parents, Erin and Michael Schyck, and my brother, Mikey, for their continuous support, inspiration, and love throughout my life. iv TABLE OF CONTENTS ABSTRACT .................................................................................................................................... ii ACKNOWLEDGMENTS ............................................................................................................. iii LIST OF TABLES .......................................................................................................................... v LIST OF FIGURES ....................................................................................................................... vi CHAPTER 1 : INTRODUCTION .................................................................................................. 1 CHAPTER 2 : EXPERIMENTAL AND THEORETICAL BACKGROUND .............................. 3 A. X-ray’s Interaction with Matter ............................................................................................. 3 B. Experimental and theoretical background of HgF4 synthesis ............................................... 5 CHAPTER 3 : EXPERIMENTAL SETUPS AND CHARACTERIZATION METHODS ........... 6 A. Diamond Anvil Cell ............................................................................................................... 6 B. Ruby as a pressure marker ..................................................................................................... 8 C. Infrared Spectroscopy ............................................................................................................ 9 D. X-ray diffraction .................................................................................................................. 12 E. X-ray absorption spectroscopy ............................................................................................. 15 F. Raman spectroscopy ............................................................................................................. 17 CHAPTER 4 : STRUCTURAL PROPERITIES OF HgF2 AT HIGH PRESSURE .................... 20 A. Purification of HgF2 by high pressure ramp process ........................................................... 20 B. HgF2 at high pressures ........................................................................................................ 23 CHAPTER 5 : INVESTIGATION OF HgF4 AT HIGH PRESSURE.......................................... 32 A. XRD characterization of irradiated HgF2 XeF2 samples ................................................ 33 B. XRD characterization of unirradiated HgF2 XeF2 samples ............................................ 39 C. IR characterization of irradiated HgF2 XeF2 samples .................................................... 43 D. Characterization of HgF2 XeF2 samples by XAS .......................................................... 44 E. X-ray induced decomposition of XeF2 ................................................................................ 46 CHAPTER 6 : CONCLUSIONS .................................................................................................. 48 CHAPTER 7 : FUTURE WORK ................................................................................................. 49 REFERENCES ............................................................................................................................. 50 CURRICULUM VITAE…………………………………………………………………………60 v LIST OF TABLES Table 3-1 Features of the CLS Far-IR beamline ........................................................................... 12 Table 3-2 Characteristic excitation and fluorescence energies of Mercury[51]. .......................... 16 Table 4-1 Observed and calculated d spacings for the fluorite-type phase of HgF2 at 0 GPa. These peaks are fit to an cubic unit cell with a = 5.5327 Å and V=169.367 Å3. .................................... 24 Table 4-2 Equation of state parameters for HgF2. Asterisk (*) represents fixed values. .............. 25 Table 4-3 Observed and calculated d spacings for the cotunnite-type phase of HgF2 at 5.6 GPa. The peaks are fit to a orthorhombic unit cell with a = 5.7678 Å, b =3.5334 Å, c = 7.1388 Å, and V= 145.490 Å3. ............................................................................................................................. 28 Table 4-4 Predicted lattice parameters and atomic positions of two candidate orthorhombic HgF2 phases at around 6 GPa. The Pnam phase is the orthorhombic cotunnite-type PbCl2