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

First-Principles Investigations on Structural, Elastic, and Thermodynamic Properties of Ce-La Alloys Under High Pressure

2014 ◽  
Vol 69 (1-2) ◽  
pp. 52-60
Author(s):  
Li-Qin Zhang ◽  
Yan Cheng ◽  
Zhen-Wei Niu ◽  
Guang-Fu Ji
Keyword(s):  
Heat Capacity ◽  
High Pressure ◽  
Thermal Expansion ◽  
Thermodynamic Properties ◽  
Electronic Properties ◽  
Ground State ◽  
First Principles ◽  
Debye Model ◽  
First Principles Calculations ◽  
Charge Densities

The structural stability, thermodynamic, elastic, and electronic properties of cerium (Ce)- lanthanum (La) alloys were investigated for different Ce/La ratios under pressure by first-principles calculations using on-the-fly (OTF) pseudopotential and general gradient approximation (GGA). The ground-state properties of lanthanum and cerium obtained by minimizing the total energy agree favourably with other work.We derived the elastic constants, bulk modulus, and shear modulus of the La-Ce alloys for different Ce/La ratios. Using the quasi-harmonic Debye model, the thermodynamic properties of the La-Ce alloys including the thermal expansion coefficient α and heat capacity Cv are successfully obtained in the temperature range from 0 K to 1000 K. Furthermore, the electronic properties such as density of states and charge densities were also studied.

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.

PHASE TRANSITION AND THERMODYNAMIC PROPERTIES OF MAGNESIUM FLUORIDE BY FIRST PRINCIPLES

2014 ◽  
Vol 28 (08) ◽  
pp. 1450026 ◽  
Author(s):  
TIAN ZHANG ◽  
YAN CHENG ◽  
ZHEN-LONG LV ◽  
GUANG-FU JI ◽  
MIN GONG
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Structural Phase ◽  
Harmonic Approximation ◽  
Electronic Density ◽  
Good Agreement

The structural stabilities, phase transitions and thermodynamic properties of MgF 2 under high pressure and temperature are investigated by first-principles calculations based on plane-wave pseudopotential density functional theory method within the local density approximation. The calculated lattice parameters of MgF 2 in all four phases under zero pressure and zero temperature are in good agreement with the existing experimental data and other theoretical results. Our results demonstrate that MgF 2 undergoes a series of structural phase transitions from rutile (P42/mnm)→ CaCl 2-type (Pnnm)→ modified fluorite (Pa-3)→ cotunnite (Pnam) under high pressure and the obtained transition pressures are in fairly good agreement with the experimental results. The temperature-dependent volume and thermodynamic properties of MgF 2 in the rutile phase at 0 GPa are presented and the thermodynamic properties of MgF 2 in the rutile, CaCl 2-type, modified fluorite and cotunnite phases at 300 K are also predicted using the quasi-harmonic approximation model (QHA) and the quasi-harmonic Debye model (QHD), respectively. Moreover, the partial density of states and the electronic density of the four phases under the phase transition are also investigated.

First Principles Investigations on the Controversy of Structural Phase Transitions in Thorium Dialuminide under Pressure

2021 ◽  
Author(s):  
Ashok Kumar Verma ◽  
Paritosh Modak
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
Structural Phase ◽  
First Principles Calculations ◽  
Structural Phase Transitions ◽  
Structural Aspects

We study the high pressure structural aspects of thorium dialuminide, ThAl2, by performing evolutionary crystal structure searches and first principles calculations. We predict a phase transition from the ambient AlB2-type...

scholarly journals Novel structural phases and the properties of LaX (X = P, As) under high pressure: first-principles study

RSC Advances ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 3058-3070
Author(s):  
Yu Zhou ◽  
Lan-Ting Shi ◽  
A-Kun Liang ◽  
Zhao-Yi Zeng ◽  
Xiang-Rong Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Pressure Range ◽  
Mechanical Stability ◽  
First Principles Study

The structures, phase transition, mechanical stability, electronic structures, and thermodynamic properties of lanthanide phosphates (LaP and LaAs) are studied in the pressure range of 0 to 100 GPa by first principles.

Orbital change manipulation metal–insulator transition temperature in W-doped VO2

2015 ◽  
Vol 17 (17) ◽  
pp. 11638-11646 ◽  
Author(s):  
Xinfeng He ◽  
Yijie Zeng ◽  
Xiaofeng Xu ◽  
Congcong Gu ◽  
Fei Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Infrared Spectroscopy ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
First Principles ◽  
Insulator Transition ◽  
First Principles Calculations ◽  
Orbital Structure ◽  
Metal Insulator Transition ◽  
Metal Insulator

Using ultraviolet-infrared spectroscopy and first principles calculations, it is revealed that changes in the orbital structure can regulate the W-doped VO2 phase transition temperature.

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