Dottorato di Ricerca in Scienze della Terra Ciclo XXVI Cancrinite-group minerals at non-ambient conditions: a model of the elastic behavior and structure evolution Ph.D. Thesis Paolo Lotti Matricola R08990 Summary Chapter 1 - Introduction……………………………………………………………………………...1 1.1 The [CAN]-framework type………………………………………………………….2 1.2 The crystal chemistry of cancrinite-group minerals………………………………….7 1.2.1 Cancrinite-subgroup minerals………………………………………………...8 1.2.2 Davyne-subgroup minerals………………………………………………….14 1.3 Natural occurrences of cancrinite-group minerals…………………………………..21 1.4 Synthetic cancrinite-group compounds……………………………………………...27 1.5 Cancrinite-group compounds in relevant technological processes………………….33 Chapter 2 - Non-ambient conditions: mineral physics and experimental techniques………………39 2.1 Temperature and pressure mineral physics………………………………………….40 2.1.1 Elastic parameters…………………………………………………………...40 2.1.2 Equations of state……………………………………………………………41 2.1.3 Thermal ( T,V)P equations of state…………………………………………...42 2.1.4 Isothermal ( P,V)T equations of state…………………………………………44 2.1.5 High-temperature and high-pressure P-V-T equations of state……………...46 2.1.6 The FE-fE plot………………………………………………………………..47 2.2 Low-temperature and high-pressure single-crystal diffraction techniques………….51 2.2.1 In situ low-temperature devices……………………………………………..52 2.2.2 In situ high-pressure devices………………………………………………...52 Chapter 3 - Cancrinite-group minerals at non-ambient conditions…………………………………63 3.1 Cancrinite-group minerals at non-ambient conditions: the state-of-the-art…………64 3.1.1 High-temperature studies on cancrinite-group compounds…………………65 3.1.2 High-pressure studies on cancrinite-group compounds……………………..68 3.2 The aim of the project: a model of the thermo-elastic behavior and structure evolution of cancrinite-group minerals at non-ambient conditions……………………………………………………………………………71 Chapter 4 - Cancrinite………………………………………………………………………………73 4.1 Cancrinite behavior at low temperature……………………………………………..74 4.1.1 Materials and experimental methods………………………………………..74 4.1.2 Results……………………………………………………………………….75 4.1.3 Discussion…………………………………………………………………...79 4.1.4 Conclusions………………………………………………………………….81 4.2 Cancrinite behavior at high pressure………………………………………………...88 4.2.1 Materials and methods……………………………………………………....88 4.2.2 Results……………………………………………………………………….90 4.2.3 Discussion…………………………………………………………………...93 4.3 Cancrinite behavior at high temperature…………………………………………….99 4.3.1 Experimental methods……………………………………………………….99 4.3.2 Results and discussion……………………………………………………...102 Chapter 5 - Vishnevite……..,……………………………………………………………………...115 5.1 Vishnevite behavior at low temperature and high pressure………………………..116 5.1.1 Materials and experimental methods………………………………………116 5.1.2 Structure refinements and high-pressure structural re-arrangement……….117 5.1.3 Results……………………………………………………………………...119 5.1.4 Discussion………………………………………………………………….122 5.1.5 Conclusions………………………………………………………………...126 II Chapter 6 - Balliranoite……………………………………………………………………………133 6.1 Balliranoite behavior at low temperature…………………………………………..134 6.1.1 Materials and experimental methods………………………………………134 6.1.2 Results……………………………………………………………………...135 6.1.3 Discussion………………………………………………………………….138 6.1.4 Conclusions………………………………………………………………...141 6.2 Balliranoite behavior at high pressure……………………………………………..148 6.2.1 Materials and experimental methods………………………………………148 6.2.2 Structure refinement protocol……………………………………………...149 6.2.3 Results……………………………………………………………………...151 6.2.4 Discussion………………………………………………………………….152 6.2.5 Conclusions………………………………………………………………...157 Chapter 7 - Davyne………………………………………………………………………………...161 7.1 Davyne behavior at low temperature………………………………………………162 7.1.1 Experimental methods……………………………………………………...162 7.1.2 Results……………………………………………………………………...164 7.1.3 Discussion………………………………………………………………….167 7.2 Davyne behavior at high pressure………………………………………………….179 7.2.1 Materials and experimental methods………………………………………179 7.2.2 Structure refinements and P-induced displacive phase transition………….180 7.2.3 Results……………………………………………………………………...183 7.2.4 Discussion………………………………………………………………….185 7.2.5 Conclusions………………………………………………………………...189 III Chapter 8 - Discussion……………………………………………………………………………..195 8.1 Isothermal elastic behavior………………………………………………………...196 8.2 Thermoelastic behavior at constant pressure………………………………………199 8.3 High-temperature behavior………………………………………………………...200 8.4 P-induced P63/m to P63 displacive phase transition……………………………….203 8.5 The deformation mechanisms of the [CAN]-framework…………………………..203 8.6 The can unit extraframework content……………………………………………...206 8.7 The channel extraframework content………………………………………………209 Chapter 9 - Conclusions…………………………………………………………………………...213 Acknowledgements………………………………………………………………………………..219 Appendix - Tables…………………………………………………………………………………221 References………………………………………………………………………………………...303 IV Chapter 1 Introduction Chapter 1 1.1 THE [CAN]-FRAMEWORK TYPE The [CAN]-framework type (Baerlocher et al. 2007) belongs to the so-called ABC-6 family of frameworks (Gies et al. 1999). In this family, the periodic building unit consists of six-membered rings of tetrahedra (S6R), not interconnected each other, arranged according to a hexagonal array (Fig. 1.1). The plane symmetry of such an arrangement is P6mm . Let us arbitrarily place the position of the ring at the coordinate (1/3,2/3) of a hexagonal cell and call it as an “A” position. Three kinds of stacking can occur: 1) the rings of new plane can be placed still at (1/3,2/3) giving rise to an “AA” stacking; 2) the new rings can be placed at (2/3,1/3) in a position arbitrarily called “B”, giving rise to an “AB” stacking; 3) the rings can be placed at (0,0) in a position called “C”, from which an “AC” stacking derives (Fig. 1.1). Then, a third plane of single six-membered rings can be stacked according to one of the three stacking options described above. If the stacking follows a periodic rule, a periodic three-dimensional framework is built up. Of the potentially infinite stacking sequences, many have effectively been found in natural minerals and/or in synthetic compounds (Baerlocher et al. 2007). The most simple sequence, the “AB” stacking, where “A” rings are centered at (1/3,2/3, z) and the “B” rings at (2/3,1/3, z), gives rise to the [CAN]-framework type (Fig. 1.2), i.e. to the framework of the cancrinite-group minerals, which are the object of the present study. Another class of widespread feldpathoids, the sodalite group, is structurally related to the cancrinite structure, as its framework ([SOD]-type) derives from an “ABC” stacking sequence. For both these groups, no superposition of the same ring type occurs. However, this is a common feature of several open-framework compounds. For example, in the [GME]-framework (AABB) of gmelinite, the [CHA]-framework (AABBCC) of chabazite, the [ERI]-framework (AABAAC) of erionite, or the [AFX]-framework (AABBCCBB) of the well-known synthetic zeolite SAPO-56. Although all these frameworks derive from different stackings of the same periodic building unit, their “secondary building-units” ( sensu Barlocher et al. 2007) and the size and relative orientation of the structural voids can be significantly different. In addition, different can be the crystal-chemical and –physical properties of the related compounds. Therefore, it is not surprising that the natural feldpspathoids and zeolites, structurally related to the ABC-6 family, are widespread over a variety of geochemical and petrological environments. Before to introduce the structural features of the [CAN]-framework type, it is worth noting that there is a series of minerals showing different ABC-6 frameworks, which are, for geochemical and petrological reasons, closely related to the proper cancrinite-group. These minerals, although sometimes grouped within the cancrinite-group in the literature, were originally defined “cancrinite-like” by Leoni et al. 2 Introduction (1979), as reviewed by Bonaccorsi and Merlino (2005). Among them there are: bystrite ([LOS], ABAC, Pobedimskaya et al. 1991), liottite ([LIO], ABABAC, Ballirano et al. 1996a), afghanite ([AFG], ABABACAC, Ballirano et al. 1997), franzinite ([FRA], ABCABACABC, Ballirano et al. 2000), tounkite ([TOL], ABABACACABAC, Rozenberg et al. 2004), farneseite ([FAR], ABCABABACBACAC, Cámara et al. 2004), giuseppettite ([GIU], ABABABACBABABABC, Bonaccorsi 2004). As previously described, the [CAN]-framework type is built from the simplest stacking sequence in the ABC-6 family: ···ABABAB···. In each plane ( e.g. the “A” plane), the six-membered rings are not interconnected to each other (Fig. 1.1) and each ring is linked to three rings in the previous (“B”) plane and to three rings in the next one (Fig. 1.2). The resulting structure is made by columns of base- sharing can units, also called “cancrinite cages”, undecahedral cages or 4 665 units according to the IUPAC recommendations (McCusker et al. 2001), where the bases correspond to the single six- membered rings perpendicular to the c-axis (S6R ⊥[0001], Fig 1.2). These columns surround iso- oriented channels, parallel to [0001] and confined by twelve-membered rings of tetrahedra (12R) (Fig 1.2). Double zigzag chains of tetrahedra ( dzc units), made by edge-sharing four-membered rings (S4R), run along the c-axis and border the single six-membered ring windows (hereafter S6R ∠[0001]) acting as joint unit between cages and channels (Fig 1.2). Therefore, as reported in the literature ( e.g. Pekov