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Abstract: The structural stability in TaSi2 was investigated by in situ angle dispersive X-ray diffraction (AD-XRD), which shows that the structure is stable even up to about 50.0GPa at room temperature. However, under high pressure and high temperature (HPHT) conditions it was revealed that TaSi2 could undergo a structural phase transition from a C40-type hexagonal phase to a metastable phase after a temperature quench from 573K at 10.6GPa. [Copyright &y& Elsevier]

The structural behaviour of Cu5Si under high-pressure (HP) has been studied by angular dispersive X-ray diffraction up to 49.9 GPa. The experimental results suggest that a pressure-induced isostructural phase transition occurs around 13.5 GPa as revealed by a discontinuity in volume as a function of pressure. The lattice parameter decreases with the pressure increasing for both low-pressure (LP) and HP phases of Cu5Si. However, a plot of the lattice parameter vs. pressure shows the existence of a plateau between 11.7 and 15.3 GPa. The bulk moduli, derived from the fitting of Birch–Murnaghan equation of state, are 150(2) GPa and 210(3) GPa for the LP phase and the HP phase of Cu5Si, respectively. A change in the electronic state of the copper is assumed to govern the observed structural phase transition. [ABSTRACT FROM PUBLISHER]

Abstract: High pressure effect on the structural polymorphy of YCu was studied based on the first principle density functional theory. The calculated values of lattice parameters are in good agreement with the available experimental results. The geometry optimization results indicate the anisotropy of the compressibility of FeB-type YCu under high pressure. It is remarkable that the compressibilities along the b- and c-axes experience an abnormality at about 3.3GPa. Energy calculation results demonstrate that YCu is stable in the FeB-type structure at low temperature and ambient pressure, which is in good agreement with the experimental results. And there exists a structural phase transition from FeB-type structure to CsCl-type structure at the transition pressure of approximate 6.7GPa. This is the quantitative theoretical prediction of structural phase transition, and it still awaits the experimental confirmation. [Copyright &y& Elsevier]

Abstract: Nb3Al, which is widely used in high field magnets, was studied under a range of pressures up to 39.5GPa using diamond anvil cell. The Nb3Al superconductor is structurally stable up to the highest pressure of the present investigation from previous reports. However, an anomaly of the compressibility beyond 19.2GPa was detected in the pressure versus volume plot. The curve of volume versus pressure shows the existence of a plateau around 18.0GPa as seen in several other highly correlated electrons systems, The observed pressure-induced isostructural phase transition was accomplished with a volume inclination without any symmetrical change (space group, Wyckoff position). The physical mechanism behind this isostructural phase transition is the interesting issue for further studies. [Copyright &y& Elsevier]

Abstract: Cr2As, which is an intermetallic compound of Cu2Sb-type with Strukturbericht designation C38 was studied under a pressure of up to 32.5 GPa at room temperature using in situ synchrotron X-ray powder diffraction with a diamond anvil cell. From the X-ray diffraction analysis, our results showed that the Cu2Sb (C38)-type phase of Cr2As undergoes a pressure-induced structural phase transition near 15.4 GPa. The high-pressure (HP) phase of Cr2As is suggested as an orthorhombic structure. No additional structural phase transition was observed up to 32.5 GPa, and the initial low-pressure (LP) Cu2Sb (C38)-type structure was recovered as the pressure was released, implying that the observed pressure-induced structural phase transformation was reversible. The pressure–volume data of Cr2As was fitted to a second-order Birch–Murnaghan equation of state, which yielded a bulk modulus of and 340 (12) GPa for the LP and the HP phases, respectively. Furthermore, the axis is more compressible than the axis for the LP phase of Cr2As. The anisotropic compressibility of the studied crystal is discussed in terms of the crystallography stacking. [Copyright &y& Elsevier]