Ab Initio Calculation of the System Cr–GaSb: A New High-Pressure Phase Containing Defects

We report on ab initio density-functional calculations of a novel spintronics-related compound CrGa2Sb2 recently synthesized under high pressure. The effect of Cr deficiency on the electronic, magnetic and optical properties of CrGa2Sb2 is considered. New X-ray structural measurements up to high pressure of 9 GPa are presented.

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High pressure phase stability, mechanical and optical properties of Ti4SiC3 compound: ab initio study

The European Physical Journal B ◽

10.1140/epjb/e2014-50358-y ◽

2014 ◽

Vol 87 (10) ◽

Cited By ~ 9

Author(s):

Zhao-Yong Jiao ◽

Shu-Hong Ma ◽

Tian-Xing Wang

Keyword(s):

High Pressure ◽

Optical Properties ◽

Ab Initio ◽

Phase Stability ◽

High Pressure Phase ◽

Ab Initio Study ◽

Pressure Phase

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The high-pressure phase transitions of silicon and gallium nitride: a comparative study of Hartree - Fock and density functional calculations

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/8/22/004 ◽

1996 ◽

Vol 8 (22) ◽

pp. 3993-4000 ◽

Cited By ~ 37

Author(s):

Ravindra Pandey ◽

Mauro Causa' ◽

Nicholas M Harrison ◽

Max Seel

Keyword(s):

High Pressure ◽

Gallium Nitride ◽

Phase Transitions ◽

Comparative Study ◽

Density Functional Calculations ◽

Density Functional ◽

High Pressure Phase ◽

Hartree Fock ◽

Pressure Phase

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Pressure-induced polymorphism in phenol

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768102018797 ◽

2002 ◽

Vol 58 (6) ◽

pp. 1018-1024 ◽

Cited By ~ 34

Author(s):

David R. Allan ◽

Stewart J. Clark ◽

Alice Dawson ◽

Pamela A. McGregor ◽

Simon Parsons

Keyword(s):

Crystal Structure ◽

High Pressure ◽

Ab Initio ◽

Density Functional ◽

Ambient Pressure ◽

Energy Difference ◽

X Ray Diffraction ◽

X Ray ◽

Pressure Melting ◽

Pressure Phase

The high-pressure crystal structure of phenol (C6H5OH), including the positions of the H atoms, has been determined using a combination of single-crystal X-ray diffraction techniques and ab initio density-functional calculations. It is found that at a pressure of 0.16 GPa, which is just sufficient to cause crystallization of a sample held at a temperature just above its ambient-pressure melting point (313 K), a previously unobserved monoclinic structure with P21 symmetry is formed. The structure is characterized by the formation of hydrogen-bonded molecular chains, and the molecules within each chain adopt a coplanar arrangement so that they are ordered in an alternating 1-1-1 sequence. Although the crystal structure of the ambient-pressure P1121 phase is also characterized by the formation of molecular chains, the molecules adopt an approximate threefold arrangement. A series of ab initio calculations indicates that the rearrangement of the molecules from helical to coplanar results in an energy difference of only 0.162 eV molecule−1 (15.6 kJ mole−1) at 0.16 GPa. The calculations also indicate that there is a slight increase in the dipole moment of the molecules, but, as the high-pressure phase has longer hydrogen-bond distances, it is found that, on average, the hydrogen bonds in the ambient-pressure phase are stronger.

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Compressibility and Phase Stability of Iron-Rich Ankerite

Minerals ◽

10.3390/min11060607 ◽

2021 ◽

Vol 11 (6) ◽

pp. 607

Author(s):

Raquel Chuliá-Jordán ◽

David Santamaria-Perez ◽

Javier Ruiz-Fuertes ◽

Alberto Otero-de-la-Roza ◽

Catalin Popescu

Keyword(s):

High Pressure ◽

Density Functional ◽

Computational Study ◽

Density Functional Theory Calculations ◽

High Pressure Phase ◽

Stable Phase ◽

Pressure Derivative ◽

Reversible Phase Transition ◽

Murnaghan Equation ◽

Pressure Phase

The structure of the naturally occurring, iron-rich mineral Ca1.08(6)Mg0.24(2)Fe0.64(4)Mn0.04(1)(CO3)2 ankerite was studied in a joint experimental and computational study. Synchrotron X-ray powder diffraction measurements up to 20 GPa were complemented by density functional theory calculations. The rhombohedral ankerite structure is stable under compression up to 12 GPa. A third-order Birch–Murnaghan equation of state yields V0 = 328.2(3) Å3, bulk modulus B0 = 89(4) GPa, and its first-pressure derivative B’0 = 5.3(8)—values which are in good agreement with those obtained in our calculations for an ideal CaFe(CO3)2 ankerite composition. At 12 GPa, the iron-rich ankerite structure undergoes a reversible phase transition that could be a consequence of increasingly non-hydrostatic conditions above 10 GPa. The high-pressure phase could not be characterized. DFT calculations were used to explore the relative stability of several potential high-pressure phases (dolomite-II-, dolomite-III- and dolomite-V-type structures), and suggest that the dolomite-V phase is the thermodynamically stable phase above 5 GPa. A novel high-pressure polymorph more stable than the dolomite-III-type phase for ideal CaFe(CO3)2 ankerite was also proposed. This high-pressure phase consists of Fe and Ca atoms in sevenfold and ninefold coordination, respectively, while carbonate groups remain in a trigonal planar configuration. This phase could be a candidate structure for dense carbonates in other compositional systems.

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