PHASE TRANSITION, ELASTIC AND THERMODYNAMIC PROPERTIES OF BERYLLIUM VIA FIRST PRINCIPLES

2013 ◽  
Vol 27 (24) ◽  
pp. 1350130 ◽  
Author(s):  
YAN CHENG ◽  
HAI-HUA CHEN ◽  
FAN-XIANG XUE ◽  
GUANG-FU JI ◽  
MIN GONG
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Intermediate Phase ◽  
Linear Thermal Expansion ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Bcc Phase

The phase transition, elastic and thermodynamic properties of beryllium (Be) have been studied at high pressures by plane-wave ultrasoft pseudopotential density functional theory (DFT) within the generalized gradient approximation (GGA). It is found that the hcp → bcc phase transition of Be occurs at 506 GPa (T = 0 K ) and occurs at 1200 K (P = 0 GPa ). The coefficients of linear thermal expansion of the hexagmal close-packed (hcp), bcc and orthorhombic Be have been calculated. The hcp → orthorhombic → bcc phase transitions do not occur in all range of pressures, that is to say, the orthorhombic Be is not an intermediate phase between the hcp and bcc Be. The obtained bulk modulus (B0) are 113.2 GPa (for hcp Be), 113.1 GPa (for bcc Be) and 70.5 GPa (for orthorhombic Be), respectively.

Thermodynamic Properties of CaSiO3 Perovskite at High Pressure and High Temperature

2009 ◽  
Vol 64 (5-6) ◽  
pp. 399-404 ◽  
Author(s):  
Zi-Jiang Liu ◽  
Xiao-Ming Tan ◽  
Yuan Guo ◽  
Xiao-Ping Zheng ◽  
Wen-Zhao Wu
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
Casio3 Perovskite ◽  
First Time

The thermodynamic properties of tetragonal CaSiO3 perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines the ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state is in excellent agreement with the observed values at ambient condition. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

THERMODYNAMIC PROPERTIES OF MgSiO3 POST-PEROVSKITE

2010 ◽  
Vol 24 (03) ◽  
pp. 315-324
Author(s):  
ZI-JIANG LIU ◽  
XIAO-WEI SUN ◽  
CAI-RONG ZHANG ◽  
LI-NA TIAN ◽  
YUAN GUO
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
High Pressures And Temperatures ◽  
First Time

The thermodynamic properties of MgSiO 3 post-perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines with ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state of MgSiO 3 post-perovskite is in excellent agreement with the latest observed values. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion, and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

First-principles investigation of the elastic and thermodynamic properties of ReC2 (Re = Ho, Nd, Pr)

2015 ◽  
Vol 29 (01) ◽  
pp. 1450256 ◽  
Author(s):  
Wen Huang ◽  
Haichuan Chen
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Lattice Constants ◽  
Generalized Gradient Approximation ◽  
Temperature Melting

The elastic and thermodynamic properties of Re C 2 (Re = Ho , Nd , Pr ) have been investigated by using the first-principles density functional theory within the generalized gradient approximation. The computed lattice constants of Re C 2 are in agreement with the experimental data. The calculated elastic constants reveal that all compounds are mechanically stable. The shear modulus, Young's modulus, Poisson's ratio σ, the ratio B/G, shear anisotropy and elastic anisotropy are also calculated. Finally, the Vicker hardness, Debye temperature, melting point and thermal conductivity have been predicted.

Structural Phase Transition and Electronic Properties of MgCe under High Pressure from First-Principles Calculations

2014 ◽  
Vol 577 ◽  
pp. 102-107
Author(s):  
Qiu Xiang Liu ◽  
De Ping Lu ◽  
Rui Jun Zhang ◽  
Lei Lu ◽  
Shi Fang Xie
Keyword(s):  
Phase Transition ◽  
Ground State ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Structural Phase ◽  
First Principles Calculations ◽  
Functional Theory

The structural stability of MgCe under high pressures has been investigated by using the first-principles plane-wave pseudopotential density functional theory within the local density approximation (LDA). The obtained results predict that MgCe in the Ba structure is predicted to be the most stable structure corresponding to the ground state, because of lowest total energy. MgCe undergoes a pressure-induced phase transition from the Ba structure to B32 structure at 36 GPa. And no further transition is found up to 120 GPa. In addition, the electronic structures of four structures of MgCe are also calculated and discussed.

First-principles study of the phonon, mechanical and thermodynamic properties of B2-phase AlY under high pressures

2017 ◽  
Vol 31 (32) ◽  
pp. 1750254
Author(s):  
Leini Wang ◽  
Zhang Jian ◽  
Wei Ning
Keyword(s):  
High Pressure ◽  
Thermodynamic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Mechanical Stability ◽  
Debye Model ◽  
Functional Theory ◽  
B2 Phase

We have investigated the phonon, mechanical and thermodynamic properties of B2-phase AlY under high pressure by performing density functional theory (DFT). The result of phonon band structure shows B2-phase AlY exhibits dynamical stability. Then, the elastic properties of AlY under high pressure have been discussed. The elastic constants of AlY increase monotonically with the increase of the pressure and all the elastic constants meet the mechanical stability standard under high pressure. By analyzing the Poisson’s ratio [Formula: see text] and the value of B/G of AlY, we first predicted that AlY undergoes transformation from brittleness to ductility at 30 GPa and high pressure can improve the ductility. To obtain the thermodynamic properties of B2-phase AlY, the quasi-harmonic Debye model has been employed. Debye temperature [Formula: see text], thermal expansion coefficient [Formula: see text], heat capacity C[Formula: see text] and Grüneisen parameter [Formula: see text] of B2-phase AlY are systematically explored at pressure of 0–75 GPa and temperature of 0–700 K.

First-principles investigation of the electronic, mechanical, and thermodynamic properties of europium carbide

2015 ◽  
Vol 93 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Wen Huang ◽  
Lijun Yang
Keyword(s):  
Thermodynamic Properties ◽  
Shear Modulus ◽  
Sound Velocity ◽  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Longitudinal Sound Velocity ◽  
Temperature Melting

The electronic, mechanical, and thermodynamic properties of europium carbide (EuC2) are investigated using first-principles density functional theory within the generalized gradient approximation. The calculated elastic constants indicate that EuC2 is mechanically stable. The shear modulus, Young’s modulus, Poisson’s ratio, the bulk modulus – shear modulus ratio, shear anisotropy, and elastic anisotropy are also calculated. Finally, we obtain the Vickers hardness, averaged sound velocity, longitudinal sound velocity, transverse sound velocity, Debye temperature, melting point, and thermal conductivity of EuC2.

First-Principles Calculations of the Structure and Magnetic Phases of FeAs2 Compound under Pressure

SPIN ◽  
2018 ◽  
Vol 08 (04) ◽  
pp. 1850016 ◽  
Author(s):  
O. Sebaa ◽  
Y. Zaoui ◽  
K. O. Obodo ◽  
H. Bendaoud ◽  
L. Beldi ◽  
...  
Keyword(s):  
Phase Transition ◽  
First Principles ◽  
Density Functional ◽  
Stable Phase ◽  
Spin Orbit Coupling ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Electronic Density ◽  
Functional Theory ◽  
Spin Ordering

Understanding of different magnetic configurations for the FeAs2 iron pnictide compound is carried out using first-principles studies based on spin density functional theory (DFT) within the generalized gradient approximation (GGA), including the spin–orbit coupling (SOC). The calculated stable phase is in the marcasite (Pnnm) with nonmagnetic spin-ordering. We find that the FeAs2 compound in the nonmagnetic (NM) marcasite phase undergoes pressure-induced phase transition to the antiferromagnetic (AFM1) marcasite phase at 12[Formula: see text]GPa, then to the AFM CuAl2 ([Formula: see text]4/mcm) phase at 63[Formula: see text]GPa. The phase transition is also accompanied by semiconducting (marcasite phase) to metallic (CuAl2 phase) transition. The calculated electronic density of states profile shows the hybridization of the Fe-3[Formula: see text] and As-4[Formula: see text] orbitals plays an important role in determining the electronic and magnetic characters of this compound. The associated phase transition results in increased Fe-3d orbitals around the Fermi energy level.

scholarly journals Insight into Physical and Thermodynamic Properties of X3Ir (X = Ti, V, Cr, Nb and Mo) Compounds Influenced by Refractory Elements: A First-Principles Calculation

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 104 ◽  
Author(s):  
Dong Chen ◽  
Jiwei Geng ◽  
Yi Wu ◽  
Mingliang Wang ◽  
Cunjuan Xia
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Debye Temperatures ◽  
Experimental Parameters ◽  
Experimental Values

The effects of refractory metals on physical and thermodynamic properties of X3Ir (X = Ti, V, Cr, Nb and Mo) compounds were investigated using local density approximation (LDA) and generalized gradient approximation (GGA) methods within the first-principles calculations based on density functional theory. The optimized lattice parameters were both in good compliance with the experimental parameters. The GGA method could achieve an improved structural optimization compared to the LDA method, and thus was utilized to predict the elastic, thermodynamic and electronic properties of X3Ir (X = Ti, V, Cr, Nb and Mo) compounds. The calculated mechanical properties (i.e., elastic constants, elastic moduli and elastic anisotropic behaviors) were rationalized and discussed in these intermetallics. For instance, the derived bulk moduli exhibited the sequence of Ti3Ir < Nb3Ir < V3Ir < Cr3Ir < Mo3Ir. This behavior was discussed in terms of the volume of unit cell and electron density. Furthermore, Debye temperatures were derived and were found to show good consistency with the experimental values, indicating the precision of our calculations. Finally, the electronic structures were analyzed to explain the ductile essences in the iridium compounds.

Thermodynamic Properties of AlNi Intermetallics under High Pressure

2011 ◽  
Vol 268-270 ◽  
pp. 275-279
Author(s):  
Hai Yan Wang ◽  
Dong Xia Xu ◽  
Jin Bang Yu ◽  
Xu Sheng Li ◽  
Qian Ku Hu
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Linear Thermal Expansion ◽  
Debye Model ◽  
Lattice Parameter ◽  
Relative Volume ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Calculated Lattice Parameter

The thermodynamic properties of AlNi are investigated by the full-potential linearized muffin-tin orbital (FP-LMTO) scheme within the generalized gradient approximation correction (GGA) in the frame of density functional theory. The calculated lattice parameter and bulk modulus are in excellent agreement with the experimental and other calculated results. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of relative volumeV/V0on pressureP, cell volumeVon temperatureT, linear thermal expansion α and specific heatCVon temperature and pressure are successfully obtained.

First-principles investigations on the elastic and thermodynamic properties of cubic ZrO2 under high pressure

2015 ◽  
Vol 26 (05) ◽  
pp. 1550056 ◽  
Author(s):  
Ning Wei ◽  
Xiaoli Zhang ◽  
Chuanguo Zhang ◽  
Songjun Hou ◽  
Z. Zeng
Keyword(s):  
High Pressure ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Debye Model ◽  
Pressure Effects ◽  
Ductile Material ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Resistance To Deformation

We have investigated the elastic and thermodynamic properties of ZrO 2 under pressure up to 120 Gpa by the plane wave pseudopotential density functional theory with the generalized gradient approximation (GGA) method. The elastic constants of ZrO 2 are calculated and meet the generalized stability criteria, suggesting that ZrO 2 is mechanically stable within this pressure range. The pressure effects on the elastic properties reveal that the elastic modulus B, shear modulus G and Young's modulus Y increase linearly with the pressure increasing, implying that the resistance to deformation is enhanced. In addition, by analyzing the Poisson's ratio ν and the value of B/G, we notice that ZrO 2 is regarded as being a ductile material under high pressure and the ductility can be improved by the pressure increasing. Then, we employ the quasi-harmonic Debye model considering the phononic effects to obtain the thermodynamic properties of ZrO 2. Debye temperature ΘD, thermal expansion coefficient α, heat capacity Cp and Grüneisen parameter γ are systematically explored at pressure of 0–80 Gpa and temperature of 0–1000 K. Our results have provided fundamental facts and evidences for further experimental and theoretical researches.

Sign in / Sign up

Export Citation Format

Share Document