We discuss the application of ab initio molecular dynamics simulations results to a variety of simple molecular systems under pressure. In particular we consider the polymerization and subsequent amorphization of C₂H₂ crystals upon compression up to 50 GPa, the determination of the ground state structure of the broken symmetry phase of H₂ in the pressure range 100-150 GPa, the fate of methane and ammonia along the isentrope of the middle ice layers of Neptune. We also discuss preliminary applications to O₂ and CO.

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First-principles calculations are performed for electronic structures of diatomic and monatomic phases of solid oxygen. At large volumes (low pressures) of diatomic phases an insulating antiferromagnetic state is the most stable. With decreasing the volume (increasing the pressure) the magnetic moment decreases and finally a paramagnetic metallic state becomes the most stable. The metallic state is realized by band overlapping. Finally it is shown that transition from β-Polonium to bcc structure in the monatomic phase will be hard to occur in the pressure region accessible by experiments.

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We present phase diagram of materials (Silicon, Carbon, and Titanium disilicide TiSi₂) obtained by the first principles and semi-empirical free-energy calculations. Phase boundary of the two solid phases of TiSi₂ was found to sensitively depend on the pressure, which explains the suppressed phase transition in the thin films where the interfacial stress is large. The Clapeyron slope of the graphite-liquid phase boundary was found to rather suddenly decrease at about 1 GPa because of the change in the liquid structure. The structural change is continuous, but becomes first-order like only at lower temperature range where the liquid is metastable.

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We propose probable synthesis paths using high pressure condition for well-crystallized energeticallyfavored structures of BC₂N heterodiamonds, and further show their expected mechanical and electronic properties, from a viewpoint of material design by first-principles calculations. The results indicate that BN/C₂ (111) superlattice is the most stable among atomically-mixed heterodiamond structures, and that compression of a graphitic superlattice at low temperature will be a promising way for the well-crystallized sample. The bulk modulus is found to be comparable to that of diamond. It is also found that the band-edge states of the superlattices dramatically change depending on the stacking orientation of boron and nitrogen.

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A new single-particle equation of the Kohn-Sham-Dirac type is derived from a relativistic current- and spin-density functional theory ( RCSDFT ), and is here applied to the calculations of the atomic structures of the rare-earth elements. Both the relativistic effects and the magnetic effects are taken into account on an equal footing, and the numerical calculation is carried out by modifying the method of Cortona et al. Because of the presence of the effective magnetic field, the degeneracies in all orbits are completely resolved like the Zeeman splittings. Total spin and orbital angular momenta over all the occupied states are shown to agree reasonably well with Hund's rules for the rare-earth ions.

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Stability and structural transformation under high pressure are investigated for polymorphs of calcium di-silicide (CaSi₂) theoretically. Using LDA calculalculaaaaation we can show that sp²-bonded structures are stabilized at high pressure against popular trigonal structure with sp³-bonded corrugated Si-planes. Our result suggests that even AlB₂ structure with flat honeycomb Si-planes, which has not been found for CaSi₂ experimentally, could be obtained under high pressure at low temperature. Characteristics of structural transformation of CaSi₂ is discussed in comparison with the graphite-diamond transformation in which sp³ bonding is selected at high pressure.

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Electronic properties of Ga and In under high-pressure conditions are investigated by using the first-principles molecular dynamics (FPMD) method with a stress calculation. As a result of calculation, critical pressures of overlapping shallow core d states and valence s states are 70 GPa for Ga and 120 GPa for In, respectively.

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The influence of the screening of Coulomb interactions in plasma on the dissociation energy of molecules is considered. For the hydrogen molecule and its molecular ion the dissociation energy doesn't essentially depend upon the screening length whereas the lowering of their ionization potentials exeeds 30%. This tendency makes more possible the ionization of hydrogen from the molecule through the molecular ion state.

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The structure of FeS-III has been solved from angle-dispersive x-ray powder diffraction data collected at 7. 5GPa and room temperature. It has a monoclinic unit cell (spacegroup P2₁/a) containing 12 formula units. The Fe-Fe network in phase III comprises 4-atom clusters and 6-, 8- and 10-member rings.

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The equations for the lattice strains produced by non-hydrostatic compression of the specimen are presented for all seven crystal systems in a form suitable for the analysis of experimental data. Examples of cubic (FeO and bcc iron) and hexagonal (hcp iron) systems are given to demonstrate that the analyses of the data give the estimates of single crystal elastic constants under high pressures. As the lattice strains can be measured at high pressures up to a few megabars using a diamond anvil cell, this approach offers an unique method of estimating the elastic constants at such high pressures. Further, this is the only method of estimating elastic constants of a phase stabilized under pressure. The article also discusses some other interesting specimen-material properties that can be derived at such high pressures.

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The structures of the deuterated hydroxides (M (OD) ₂; M=Mg, Ca, Mn, Ni, Co) have been refined using the Rietveld method and neutron powder diffraction data collected at high pressure. There is no statistically significant increase in the O-D interatomic distance at increased pressure while the hydrogen bonding interaction D. . . O increases as this distance decreases and the O-D. . . O angle increases. The intramolecular O-D bond valences, determined indirectly from the intermolecular D. . . O distances, decrease steadily for all materials as pressure is increased.

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We review some results recently obtained using the Paris-Edinburgh cell for high pressure neutron studies up to 25 GPa, both structural and lattice dynamical studies: Low temperature (85 K) structural studies on recovered D₂O ice VIII in the pressure range 0-7 GPa, experiments to 23 GPa to resolve the high pressure structure of YbD₂, and inelastic neutron scattering experiments on single cristalline Ge and Zn to study their transverse acoustic phonon frequencies to 10 GPa.

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Neutron scattering experiments under high pressure revealed the existence of quite novel magnetic structures in CeP at low temperatures. They are characterized by the formation of a lattice of 2μ_B Ce ferromagnetic layers, inside of which Γ₇ Ce layers are sandwiched and orders antiferromagnetically rather independently. The period of the 2μ_B Ce lattice becomes shorter with increasing pressure, and at the pressures above 1. 7 GPa, the magnetic structures become quite similar to those seen in CeSb at ambient pressure. It indicates that the electronic structure of CeP becomes closer to that of CeSb under high pressure. The present results provide useful information to understand common physics in the typical low-carrier system Ce-monopnictides.

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The high-pressure structural phase transformations in a heavy rare earth metal lutetium (Lu) were studied by energy dispersive x-ray diffraction at room temperature using a synchrotron source in a diamond anvil cell. A new phase transition Sm-type→double-h. c. p was observed at 45±5 GPa. Distorted f. c. c phase was observed at megabar pressure range. Crystal structure data is presented to 270 GPa and results are discussed within the framework of s→d electron transfer under high pressures.

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The phase diagram of samarium has been studied by in situ synchrotron X-ray diffraction with a diamond anvil cell (DAC) up to temperatures of 800 K and up to pressures of 27 GPa. Equilibrium lines between the structures dhcp, fcc and distorted fcc were defined and a triple point was located at 11. 3 GPa and 345 K. A close examination of diffraction spectra has shown that the distorted fcc phase could not be represented by a rhombohedral crystal system inside its whole domain of stability. The experimental P-V-T data were fitted to a thermal-pressure model and the values for bulk modulus and thermal expansivity were obtained.

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The high-pressure structural phase transformations in gadolinium (Gd) were studied by energy-dispersive x-ray diffraction up to 118 GPa at room temperature using a synchrotron source. Gadolinium undergoes five transitions: h. c. p→Smtype→double-h. c. p→f. c. c→distorted f. c. c→b. c. m (body-centered monoclinic), with increasing pressures. The last transition to b. c. m occurs at 59±2 GPa, accompanied by a volume collapse of about 5%. We suggest that this low-symmetry structure and volume collapse in gadolinium is analogous to the well-known electronic transition in cerium metal related to loss of magnetic moment and eventual delocalization of f-shell under pressure.

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The structural pressure dependence of strontium has been studied using angle-dispersive powder diffraction techniques with the image plate detector system. The two-dimensional diffraction data has allowed the clear identification of an accompanying minor phase in the Sr-III stability range which has enabled the structure of Sr-III to be assigned correctly as that of β-tin. The structural conformation and atomic coordination are very similar to those of β-Sn and of the high-pressure β-tin phases of Si and Ge. Sr is the first non group-IV element to be shown to have the “ideal” β-tin structure.

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Recent experimental results on the structural properties of expanded fluid Se using X-ray diffraction and XAFS techniques are described. The energy-dispersive X-ray diffraction measurements have been carried out up to the supercritical region including the semiconductor-metal (SC-M) transition region. We have revealed that the twofold coordinated structure is largely preserved even in the metallic region and the bond shortening occurs on the SC-M transition, which has been confirmed by the XAFS measurement. On the basis of these findings we propose the idea that the existence of the small chain molecule with the planar zig-zag conformation may cause the transition to the metallic state.

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X-ray diffraction for liquid Rb and liquid Na has been measured under pressure up to 6 GPa using synchrotron radiation. Volume dependences of static structure factor S (Q) and pair distribution function g (r) were obtained to the volume range v (=V/V₀) of 0. 52 for liquid Rb and to v of 0. 73 for liquid Na to investigate the effect of the electronic change on the structure of liquid metals. With increasing pressure, the peaks of S (Q) of both liquid Rb and liquid Na shift towards higher Q, and the heights of the first peak increase. These volume dependences of the structural data are compared with those for other metals under pressure and expanded fluids.

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The high pressure phase of Te_{0. 4}Se_{0. 6} can be quenched to the atmospheric pressure, and its structure was determined from single crystalline X-ray diffraction measurement. It has a monoclinic (m-) lattice with 6 atoms in a unit cell, and has a puckered layer structure containing planer zigzag chains with period 3. The zigzag chain has the bond sequence of . c-short-short-long-. c. Moreover, the superlattice structure with a unit cell size of 9 lattice constants along the baxis was found. We also detennined the structure of Tei_1-xSe_x mixtures in the whole concentration range (0≤x≤1) under high pressure utilizing the structural information obtained from the pressure-quenched m-Te_{0. 4}Se_{0. 6}. In. the Se-rich region (0. 6≤x≤1), it is observed that t- or a-Te_1-xSe_x is transformed into the monoclinic structure with 6 atoms in a unit cell (M-I phase). By application of pressure above 20GPa, the M-I phase is transformed into the monoclinic structure with 4 atoms in a unit cell (M-II phase). On the other hand, in the Te-rich region (0≤x≤0. 5), t-Te_1-xSe_x is transformed directly into the M-II phase without passing through M-I phase.

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EXAFS measurements on Te k-edge were carried out on crystalline and liquid Te under high pressure and temperature up to 2. 4 GPa and 823K using a large volume Paris-Edinburgh press. The pressure dependence of the first and second nearest neighbor distances and that of the mean-square displacements were obtained. The results were discussed in connection with pressure dependence of intra- and inter-chain bonding of Te.

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High pressure thermal analysis and differential thermal analysis have been developed for detecting phase transitions in an MA-8 type apparatus. By using these methods, the melting and freezing of gold was investigated at 12 GPa. We observed the latent heat signal of gold both on melting and freezing processes, and determined the melting temperature at 1868±10 K. This temperature is lower by about 60 K than the extrapolation of the previous experiments by using the Kraut-Kennedy equation. We interpreted this discrepancy to be due to the pressure effect on the emf of the W-3%Re/W-25%Re thermocouple.

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High pressure and temperature behavior of stoichiometric FeS (troilite) was studied up to 16GPa and 800°C, and the phase diagram of FeS was determined. There were found four stable phases; the troilite phase, the hexagonal phase, the NiAs type phase and the high pressure phase with a monoclinic cell. Some remarkable phenomena were also observed in the stable region of the hexagonal phase near the phase transition to the monoclinic phase; convergence of iso c/a curves to the boundary, an inflection in the compression curve at 300°C, and a very small coefficient of cubical expansion. These results suggested an electronic transition of the hexagonal phase between 6 and 8GPa. The transition could explain an anomaly in the boundary between the hexagonal phase and the monoclinic high pressure phase.

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Energy-dispersive x-ray diffraction studies at the Cornell High Energy Synchrotron Source were made to 202 GPa on MgSe which was found to undergo a phase transformation from the rocksalt to the seven-fold coordinated FeSi (or AuBe) structure with new peaks clearly evident at 99 GPa and internal position parameters continuing to change to the highest pressure. This is the first phase transition observed in the three magnesium chalcogenides which have the rocksalt structure at atmospheric pressure (MgSe, MgS and MgO) and may have important implications for transitions of MgO and MgS. The internal atomic positions u and w were accurately obtained as a function of pressure. This is the first accurate determination of internal atom positions above one megabar and above two megabars . The equation of state over the entire range obeyed a Birch equation with B_o = 62. 8± 1. 6 GPa and B_o' = 4. 1 ± 0. 1.

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The equilibrium pressure of hydrogen gas above solid face centered cubic (fcc) phase of chromium hydride has been determined at 150°C. As compared to the hexagonal close packed (hcp), chromium hydride plateau for the a+β phase region has been found to be lower by about 500 bars and equal to 0. 25 ± 0. 01 GPa. The search for possible pressure induced phase transition from the fcc to the hcp structure has been unsuccessful up to 37 GPa. The compressibility of the fcc hydride is similar to that of the hcp phase, showing pressure independence of the hydrogen volume in the metal lattice, and confirming the general rule observed in transition metal hydrides.

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The pressure dependence of the longitudinal acoustic mode corresponding to the elastic constant C₃₃ of the matlockite layered ionic compounds BaFX (X= Cl, Br or I) has been studied by Brillouin spectroscopy in a diamond anvil cell. All the measurements have been performed up to 20 GPa. The difference of the elastic response between the BaFX compounds is attributed to the distortion of the X electron charge density of the highly polarizable anions. This phenomenon is related to the large static dipole at the X anion and involves an energy contribution U_pol which seems to stabilize the layered structure.

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High pressure in situ X-ray diffraction measurements have been carried out using Drickamer-type high pressure apparatus. Observations were made in two independent directions relative to the compression axis. Observed strains varied systematically in the two directions depending on the Miller indices of the diffraction lines. These systematic variations can be explained by the combined effect of uniaxial compression and the elastic anisotropy of crystals. Present results indicate that careful analysis is required to derive pressure value and equation of state from in situ X-ray diffraction study.

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New developments of the imaging plate diffraction system at beamline X17B1 of the NSLS at Brookhaven National Laboratory for high pressure studies are reported here. Time resolved diffraction patterns can be recorded on an imaging plate by translating the plate in this system. This system was used to observe the olivine-spinel phase transformation in fayalite. The result demonstrates that the phase transformation relaxes stress stored in the sample. Some diffraction peaks of spinel phase, e. g. (400) and (440), were observed to appear prior to the others.

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High-pressure and high-temperature experiments on Zn₃ (PO₄) 4H₂O (Hopeite) and Zn/Ca phosphates have been carried out using the MAX 80 high pressure equipment. Fitting of Murnaghan's equation of state to the experimental data has been used to obtain the bulk modulus and its pressure derivative for Hopeite. Recrystallization of Zn/Ca phosphates at increasing temperature has been demonstrated.

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Synchrotron x-ray diffraction study of SnI₄ establishes a rich sequence of high-pressure structural transitions; 1st crystalline phase - 2nd crystalline phase - amorphous state - 3rd crystalline phase. Both metallization and amorphization proceed in the newly found 2nd phase stable above 7. 2 GPa. The 3rd crystalline phase exhibits a simple diffraction pattern that can be indexed only with the fcc lattice with the nearest interatomic distance of 3. 003±0. 001 Å at 61 GPa. This short distance is taken as evidence for pressure-induced dissociation of the SnI₄ molecules.

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Structure analysis has been performed on permanently densified lithium silicate glasses by means of Raman scattering and ultraviolet (uv) reflection spectra. Higher energy shifts of Raman bands at around 450 and 580 cm^-1 and lower energy shift of first uv reflection band were found after densification. It is deduced that these shifts are due to the decrease of Si-O-Si bond angle and the increase of Si-O bond length. The decrease of the magnitude in densification and these band shifts with lithium concentration might be due to obstruction of the structural change by lithium ions.

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The effect of pressure on the ionic conductivity of a lithium fast ion glass of chemical formula (B₂O₃) ₅ (Li₂O) ₃ (LiBr) ₂ has been measured at pressures from 5 to 24kbar at a fixed temperature of 326°C and from 200 to 500°C at a pressure of 5kbar. Complex impedance plots were used to model the equivalent circuit. It was found that two parallel RC circuits in series gave a satisfactory description of the data. One of these resistances was found to remain constant with pressure increase while the other increased monotomically. The activation energy for this process at 5kbar was found to be 0. 77eV. Our data are broadly in line with our predictions based on a modified random network model for the glass structure.

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X-ray diffraction experiments on the molten iron sulfide, FeS, were conducted up to 5 GPa by using synchrotron radiation. The correlation function g (r) for molten FeS was obtained just above the melting point. The near-neighbor structure of molten FeS does not change with pressure up to 5 GPa. The average nearest-neighbor distance is about 2. 4 Å, which is correspond to the atomic distance between Fe and S. The average coordination number is about six. In FeS melt, Fe and S atoms surround each other with an octahedral coordination in near-neighbor region.

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Electrical resistance measurements, x-ray diffraction and Raman scattering experiments have been carried out under high pressure for Se allotropies. α-monoclinic Se showed a transition to the metallic state at 12 GPa, which was considerably lower than 23 GPa of trigonal Se. Corresponding to the metallization, a structural transition to a new high-pressure phase, which could not be explained by any metallic phase of Se reported previously, was observed in α-monoclinic Se. Raman data supported this result. In amorphous Se, crystallization was observed at 12 GPa. The diffraction pattern after crystallization was explained as the coexistence of the new high-pressure phase and trigonal Se. These results have established the double nature of the sequence of the structure in the pressure-induced phase transition of Se.

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Inter- and intramolecular distances in tellurium have been investigated at pressure up to 20 GPa by the Rietveld analysis. Previously reported phase transitions from Te-I to Te-II, from Te-II to Te-III, and from Te-III to Te-IV are observed at 4 GPa, 7 GPa, and 11 GPa, respectively. In the Te-II and Te-III phases, with increasing pressure, not only four intealayer bond lengths but also one interlayer distance approach continuously to the same bond length, 3A, which is equal to the interatomic distance in the next Te-IV phase. This suggests that bonding character changes continuously from covalent character to metallic one with pressure.

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The high pressure structures of AX₂ compounds have been refined in situ up to 60 GPa in a diamond anvil cell with an imaging plate in the angle dispersive mode using a low power laboratory x-ray tube and/ or synchrotron radiation. Results for GeO₂ obtained using both sources are compared. Under the same conditions (pressure, hydrostaticity, completion of phase transformations), the refinements by the Rietveld method yielded identical atomic positions and cell parameters. A structure map of the AX₂ compounds as a function of the coordination number has been established. The transition pathways depend on the filling of the d orbitals.

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Techniques for the measurement and modelling of uniaxial preferred orientation in samples at high-pressure are presented. The experimental techniques for collecting suitable data for preferred orientation modelling are described, along with details of the data analysis. Examples are taken from the study of preferred orientation in II-IV semicondutors.

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The room tempearture equations of state of the metallic hydrides NiH_x and ReH_x have been studied to 123 GPa and of the nonmetallic hydrides AIH₃/AID₃ to 53 GPa by means of x-ray diffraction in a diamond anvil cell. The partial hydrogen volume in ALH₃/AlD₃ is found to reduce to that characteristic of metallic hydrides at∼47 GPa. The evolution of the partial hydrogen volume with pressure in the metallic hydrides is discussed in light of existing empirical models.

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GaAs and ZnTe have long been reported to have very different high-pressure structures. In this paper we report a previously unidentified high-pressure phase of GaAs found on pressure decrease from GaAs-II. The phase has a 4-fold coordinated cinnabar structure very similar to that of ZnTe-II. Although no evidence of this phase is seen on pressure increase, detailed comparisons with ZnTe suggest cinnabar GaAs is an equilibrium phase. The observation of cinnabar-GaAs, and our recent observations of GaAs-II and ZnTe-III as having the same orthorhombic Cmcm structure, reveals that these materials in fact behave very similarly at high pressure

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In-situ neutron single crystal diffraction experiments on KH₂PO₄ (KDP) are reported. They were performed in a clamped pressure cell developed for the use in standard He-flow cryostats. The details of the structure of KDP in the paraelectric phase close to the ferroelectric phase transitionT_c at a pressure of 1. 7 GPa and 20K were established. The resulting H. . . H separation δ in the disordered H-bond is 0. 26 (2) Å with a corresponding O. . . O distance of 2R=2. 446 (3) Å. These numbers deviate towards larger values from the established linear relationship of δ and 2R versus T_c.

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X-ray diffraction, dielectric constant measurement, and microscopic observation were carried out on antiferroelectric PbZrO₃ under high pressures up to78, 22, and 48 GPa, respectively, at room temperature. By x-ray diffraction analyses, it was clearly recongnized that an orthorhombic ambient-pressure phase transforms to a monoclinic phase at around 37 GPa, and then again to a slightly different monoclinic phase above 75GPa. A large anomaly in the dielectric constant was observed at around 19 GPa, which strongly suggests the appearance of ferroelectricity in PbZrO₃ at high pressure. Optical observation showed that the color changes from pale yellow into thin red at around 19 GPa and then further to black at around 37 GPa. The former change is associated with the dielectric anomaly and the latter with the phase transition to a monoclinic phase discovered by x-ray diffraction.

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The phases of cerium above 5GPa have been studied using angle-dispersive powder diffraction techniques. With filings of Ce, a C-face-centred monoclinic structure with four atoms per unit cell is obtained between 5 and 12GPa. Heating to 373K for many hours yields the known α-U phase. With a single cut piece as a sample, the α-U phase is obtained at RT.

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On the basis of the results of the diffraction studies by the present authors and those published in the literature, new structural systematics of the high pressure phases of the Group VB elements are proposed, in which the general transition sequence is expressed as rhombohedral A7 - (distorted) primitive simple cubic- distorted body-centered-cubic-body-centered-cubic. Investigation of the atomic arrangements of the high pressure phases shows that the network of the densest atomic planes changes gradually through the transition sequence.

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The pressure-induced phase transitions and compressibility of Cd_1-xZn_xTe (0 ≤x≤ 0. 55) have been investigated to a pressure of 11 GPa. The B3-to-B 1 transformation shows a linear increase from 3. 4 GPa to 7. 0 GPa as the mole fraction of Zn varied from 0 to 55%.

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Pressure-induced transitions have previously been observed at room temperature in all the alkaline chalcogenides except MgS, MgO, BeS and BeO. This paper reports on studies to 96 GPa on BeS in which a phase transformation from the four-fold zincblende structure occurs at 51 ± 8 GPa to the six-fold nickel arsenide structure, which persists to the highest pressure studied. The equation of state is given.

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The effects of particle sizes in the nanometer range on pressure-induced phase transitions of PbS have been investigated using energy-dispersive x-ray diffraction of synchrotron-wiggler radiation. Compared to bulk crystals, the onset of transition pressure showed an increase with decreasing particle size. The results also show a reduced b-axis lattice parameter for the high pressure orthorhombic phase, as compared to the bulk PbS.

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The high pressure X-ray diffraction pattern of AgGaTe₂ chalcopyrite semiconductor has been measured up to 18GPa. It is found that the first phase transition occurred at 3. 05±0. 05GPa and the chalcopyrite phase persists up to 5. 4GPa. The Rietveld analysis for the X-ray pattern recorded at 5. 4GPa shows the coexistence of the disordered tetragonal structure (P4) and the disordered orthorhombic structure (Cmcm).

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We have performed the single crystal X-ray structure analysis of the three-dimensional halogen-bridged mixedvalence compound, Cs₂Au^IAu^IIICl₆ under high pressures up to 18 GPa. The high pressure apparatus used is a diamond-anvil-cell with helium gas as an inert and hydrostatic pressure-transmitting medium. The pressure dependence of the unit cell parameters indicates a structural phase transition from tetragonal to cubic at 12. 5 GPa. The high pressure phase has a space group, Pm3m.

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Single crystal of yttrium-zinc intermetallic compound Y₂Zn₁₇ have been synthesized from the elements by means of high-pressure and high-temperature methods in a modified Belt type apparatus (h-BN capsule, 3. 5GPa, 1700°C, and subsequent release of high pressure). Y₂Zn₁₇ crystallizes in the hexagonal system with lattice constants a=8. 9709 (8) Å, c=13. 1386 (8) Å, c/a=1. 4646, space group R 3 m (No. 166), and Z=3. Final residuals after refinement against F² were R₁=0. 0270, ωR₂=0. 0612 and S=1. 239 for 23 parameters and all 237 unique data. Y₂Zn₁₇ adopts Th₂Zn₁₇-type structure.

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Phase relations of the Cd-Sn system at various pressures up to 7 GPa are investigated by means of isobaric measurement of electrical resistance. New phase boundaries caused by appearance of high pressure phases are suggested in the Sn-rich side above 3 GPa and Cd-rich side above 5 GPa. Pressure-temperature sections of the three-dimensional phase diagram of the Cd-Sn alloys are proposed.

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