Theoretical Study of a new Transition Sequence in III-V Compounds: High-Pressure Phases of InSb

1990 ◽  
Vol 193 ◽  
Author(s):  
Alberto García ◽  
Marvin L. Cohen ◽  
S. B. Zhang
Keyword(s):  
High Pressure ◽  
Total Energy ◽  
First Principles ◽  
Theoretical Study ◽  
Hexagonal Phase ◽  
Structural Models ◽  
Zero Temperature ◽  
Transition Sequence ◽  
Transition Paths ◽  
Bcc Phase

ABSTRACTA detailed study of the pressure-induced phase transitions at zero temperature in InSb up to 40 GPa using a first-principles pseudopotential total-energy method is presented. In addition to InSb(I) (cubic) and (II) (polar β-Sn), we identify InSb(III) as a hexagonal phase (found earlier for GaSb) and (VI) as a polar bcc phase in agreement with recent experiments. New structural models, orthorhombic polar β-Sn and body-centered orthorhombic, are proposed as candidates for the InSb(IV) and (V) phases based on total-energy minimizations. These findings are compared with recent results for GaAs to illustrate the trends in transition paths among III-V compounds.

Theoretical Study of High Pressure Metallic Hydrogen

1990 ◽  
Vol 193 ◽  
Author(s):  
Troy W. Barbee ◽  
Alberto García ◽  
Marvin L. Cohen
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Transition Temperature ◽  
First Principles ◽  
Theoretical Study ◽  
Hexagonal Phase ◽  
Temperature Phase ◽  
Superconducting Transition ◽  
Zero Temperature ◽  
Metallic Hydrogen

ABSTRACTA study of the zero temperature phase transitions in hydrogen under megabar pressures using a first-principles total-energy method is presented. An anisotropic primitive hexagonal phase is found to be particularly stable relative to other monatomic phases for pressures between 4 and 8 megabars. Calculations of the vibrational frequencies show that this phase is unstable with respect to a distortion tripling the unit cell along the c-axis. Results for this distorted hexagonal phase will be presented, including a calculation of its superconducting transition temperature Tc.

scholarly journals First-Principles Calculations of High-Pressure Physical Properties of Ti0.5Ta0.5 Alloy

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 796
Author(s):  
Fang Yu ◽  
Yu Liu
Keyword(s):  
High Pressure ◽  
Physical Properties ◽  
First Principles ◽  
Theoretical Study ◽  
Applied Pressure ◽  
Lattice Parameter ◽  
Physical Parameters ◽  
First Principles Calculations ◽  
Analysis Method ◽  
Metallic Bond

In this paper, an in-depth theoretical study on some physical properties of Ti0.5Ta0.5 alloy with systematic symmetry under high pressure is conducted via first-principles calculations, and relevant physical parameters are calculated. The results demonstrate that the calculated parameters, including lattice parameter, elastic constants, and elastic moduli, fit well with available theoretical and experimental data when the Ti0.5Ta0.5 alloy is under T = 0 and P = 0 , indicating that the theoretical analysis method can effectively predict the physical properties of the Ti0.5Ta0.5 alloy. The microstructure and macroscopic physical properties of the alloy cannot be destroyed as the applied pressure ranges from 0 to 50GPa, but the phase transition of crystal structure may occur in the Ti0.5Ta0.5 alloy if the applied pressure continues to increase according to the TDOS curves and charge density diagram. The value of Young’s and shear modulus is maximized at P = 25   GPa . The anisotropy factors A ( 100 ) [ 001 ] and A ( 110 ) [ 001 ] are equal to 1, suggesting the Ti0.5Ta0.5 alloy is an isotropic material at 28 GPa, and the metallic bond is strengthened under high pressure. The present results provide helpful insights into the physical properties of Ti0.5Ta0.5 alloy.

A Theoretical Study of p-Type Doping of ZnO: Problems and Solutions

2001 ◽  
Vol 666 ◽  
Author(s):  
Yanfa Yan ◽  
S.B. Zhang ◽  
S.J. Pennycook ◽  
S.T. Pantelides
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Theoretical Study ◽  
Energy Calculations ◽  
Defect Complexes ◽  
New Approaches ◽  
Impurity Defect ◽  
Problems And Solutions ◽  
P Type ◽  
Made In

ABSTRACTWe present results of a comprehensive set of first-principles total-energy calculations of native and impurity-defect complexes in ZnO and use these results to elucidate the problems that occur in efforts to achieve p-type doping. The analysis naturally leads to new approaches that are likely to overcome the difficulties. The results provide detailed explanations of recent puzzling observations made in attempts to produce p-type ZnO.

scholarly journals THEORETICAL STUDY OF Si and N ADSORPTION ON THE Si-TERMINATED SiC(001) SURFACE

1999 ◽  
Vol 06 (06) ◽  
pp. 1143-1150
Author(s):  
L. PIZZAGALLI ◽  
A. CATELLANI ◽  
G. GALLI ◽  
F. GYGI ◽  
A. BARATOFF
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
First Principles ◽  
Theoretical Study ◽  
Structural Models ◽  
Inert Substrate ◽  
Dynamics Simulations ◽  
First Principles Molecular Dynamics

We report the results of first principles molecular dynamics simulations of the adsorption of Si and N atoms on a Si-terminated p(2×1) SiC(001) surface. In particular, we discuss different structural models for the Si-rich (3×2) surface, and the adsorption of 1/8, 1/2 and 1 monolayer nitrogen on the p(2×1) surface. Our simulations show that a SiC(001)-p(2×1) surface covered by a nitrogen monolayer is an inert substrate which inhibits growth.

High-Pressure Third-Order Elastic Constants of MgO Single Crystal: First-Principles Investigation

2019 ◽  
Vol 74 (5) ◽  
pp. 447-456
Author(s):  
Jianbing Gu ◽  
Chenju Wang ◽  
Bin Sun ◽  
Weiwei Zhang ◽  
Dandan Liu
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Total Energy ◽  
Elastic Constants ◽  
First Principles ◽  
Predictive Ability ◽  
Theoretical Method ◽  
Third Order ◽  
Third Order Elastic Constants ◽  
First Time

AbstractHigh-pressure third-order elastic constants of materials have rarely been investigated experimentally and theoretically to date, so the predictive ability of the method of the volume-conserving, homogeneous deformations based on the first-principles total-energy calculations is tested for the first time in this work. Using this approach, the high-pressure third-order elastic constants ${C_{111}}-3{C_{112}}+2{C_{123}}$, ${C_{111}}/2+3{C_{112}}+{C_{123}}$, ${C_{144}}-{C_{155}}$, and C456 of the MgO single crystal are obtained successfully. Meanwhile, the reliability of this method is also verified by comparing the calculated structural properties and high-pressure second-order elastic constants of the MgO single crystal with the available experimental results and other theoretical predications. Results not only indicate the accuracy of our calculations but also reveal the feasibility of the present theoretical method. It is hoped that the present theoretical method and predictions on the high-pressure third-order elastic constants of the MgO single crystal would serve as a valuable guidance or reference for further related investigations.

THE ${\rm{Si}} (111)\mbox{-}(\sqrt{3} \times \sqrt{3})$R30°-Ag AND -Au SURFACE STRUCTURES FROM FIRST PRINCIPLES CALCULATIONS

1993 ◽  
Vol 07 (12) ◽  
pp. 787-795
Author(s):  
Y.G. DING ◽  
C.T. CHAN ◽  
K.M. HO
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Theoretical Calculations ◽  
Structural Models ◽  
Small Variation ◽  
Surface Structures ◽  
First Principles Calculations ◽  
Structural Details ◽  
Electronic And Structural Properties ◽  
Stm Images

The electronic and structural properties of the [Formula: see text]R30°- Ag and Au surfaces are investigated using first-principles total energy calculations. The structures of Au and Ag are in fact quite similar and belong to the same class of structural models. However, small variation in the structural details can give rise to quite different observed STM images, as revealed in the theoretical calculations.

Phase Transition and ThermodynamicProperties of OsN2 under High Pressure

2013 ◽  
Vol 401-403 ◽  
pp. 660-662
Author(s):  
Zhi Jian Fu ◽  
Li Jun Jia ◽  
Wei Long Quan
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Thermal Expansion ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Fluorite Structure ◽  
First Principles Calculations ◽  
Zero Temperature

The lattice parameters, phase transition, and thermodynamic properties of OsN2in pyrite and fluorite structure are investigated by first-principles calculations. The pressure and temperature induced phase transitions of OsN2from fluorite structure to pyrite structure have been obtained. It is found that the transition pressure of OsN2at zero temperature is 158.2 GPa, and there exists no transition temperature. In addition, the thermal expansion, the Debye temperature, and the Grüneisen parameter in diverse pressures and temperatures about these two structures have also been obtained. Key words: transition phase; thermodynamic properties; OsN2PACS numbers: 71.15.Mb, 64.70.Kb

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