First-Principles Predictions of Elasticity and Phase Transitions in High Pressure SiO2and Geophysical Implications

2013 ◽  
pp. 425-431 ◽  
Author(s):  
Ronald E. Cohen
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
First Principles

Crystal structure, compressibility and possible phase transitions in \boldvarepsilon-FeSi studied by first-principles pseudopotential calculations

1999 ◽  
Vol 55 (4) ◽  
pp. 484-493 ◽  
Author(s):  
Lidunka Vočadlo ◽  
Geoffrey D. Price ◽  
I. G. Wood
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
Stable Phase ◽  
Third Order ◽  
First Derivative ◽  
Pseudopotential Calculations ◽  
Cscl Type ◽  
Murnaghan Equation

An investigation of the relative stability of the FeSi structure and of some hypothetical polymorphs of FeSi has been made by first-principles pseudopotential calculations. It has been shown that the observed distortion from ideal sevenfold coordination is essential in stabilizing the FeSi structure relative to one of the CsCl type. Application of high pressure to FeSi is predicted to produce a structure having nearly perfect sevenfold coordination. However, it appears that FeSi having a CsCl-type structure will be the thermodynamically most stable phase for pressures greater than 13 GPa. Fitting of the calculated internal energy vs volume for the FeSi structure to a third-order Birch–Murnaghan equation of state led to values, at T = 0 K, for the bulk modulus, K 0, and for its first derivative with respect to pressure, K 0′, of 227 GPa and 3.9, respectively.

scholarly journals High-pressure phase transitions in rubidium and caesium hydroxides

2016 ◽  
Vol 18 (24) ◽  
pp. 16527-16534 ◽  
Author(s):  
Andreas Hermann
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
Phase Evolution ◽  
High Pressure Phase ◽  
First Principles Calculations ◽  
Pressure Phase

First-principles calculations on the phase evolution of RbOH and CsOH under compression suggest new high-pressure phases in both compounds.

Phase transitions of BaCO3 at high pressures

2008 ◽  
Vol 72 (2) ◽  
pp. 659-665 ◽  
Author(s):  
S. Ono ◽  
J. P. Brodholt ◽  
G. D. Price
Keyword(s):  
Phase Transition ◽  
Experimental Study ◽  
High Pressure ◽  
Phase Transitions ◽  
Bulk Modulus ◽  
First Principles ◽  
High Pressures ◽  
Ambient Conditions ◽  
The Stability ◽  
Previous Experimental Study

AbstractFirst-principles simulations and high-pressure experiments were used to study the stability of BaCO3 carbonates at high pressures. Witherite, which is orthorhombic and isotypic with CaCO3 aragonite, is stable at ambient conditions. As pressure increases, BaCO3 transforms from witherite to an orthorhombic post-aragonite structure at 8 GPa. The calculated bulk modulus of the post-aragonite structure is 60.7 GPa, which is slightly less than that from experiments. This structure shows an axial anisotropicc ompressibility and the a axis intersects with the c axis at 70 GPa, which implies that the pressure-induced phase transition reported in previous experimental study is misidentified. Although a pyroxene-like structure is stable in Mg- and Ca-carbonates at pressures >100 GPa, our simulations showed that this structure does not appear in BaCO3.

First Principles Study of High Pressure Phase Transitions in ThN and UN

2011 ◽  
Author(s):  
P. Modak ◽  
Ashok K. Verma ◽  
Alka B. Garg ◽  
R. Mittal ◽  
R. Mukhopadhyay
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
High Pressure Phase ◽  
First Principles Study ◽  
Pressure Phase

STRUCTURAL PHASE TRANSITIONS AND MECHANICAL PROPERTIES OF OsO2 UNDER HIGH PRESSURE

2010 ◽  
Vol 24 (22) ◽  
pp. 4269-4279 ◽  
Author(s):  
YONGCHENG LIANG ◽  
ANHU LI ◽  
QIUHONG SONG
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
Structural Phase ◽  
Fluorite Phase ◽  
Structural Phase Transitions ◽  
Pseudopotential Calculations ◽  
Excellent Candidate ◽  
High Bulk

The structural phase transitions, mechanical properties and electronic structures of OsO 2 under high pressure are systemically investigated by the first-principles plane-wave basis pseudopotential calculations. The possible pressure-induced transition sequence in OsO 2 may be the rutile, pyrite and fluorite phases, and the stable CaCl 2 structure is not found. The fluorite phase has high bulk modulus (355.3 GPa), large shear modulus G (267.9 GPa), and huge elastic constant C44 (292.7 GPa), and consequently is an excellent candidate of superhard materials. Crystal structures, valence electron densities, band structures, DOS and PDOS of the rutile, pyrite and fluorite phases of OsO 2 have also been carefully analyzed to elucidate their mechanical properties.

High-pressure phase transitions in NaBH4 from first-principles calculations

2011 ◽  
Vol 248 (5) ◽  
pp. 1139-1142 ◽  
Author(s):  
Chunye Zhu ◽  
Yanhui Liu ◽  
Fubo Tian ◽  
Tian Cui
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
High Pressure Phase ◽  
First Principles Calculations ◽  
Pressure Phase
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