Atomistic modeling based on the accurate first-principles method is used to investigate the lattice parameter, elastic constant, elastic modulus including bulk modulus （B） and shear modulus （G）, Poisson＇s ratio, ...Atomistic modeling based on the accurate first-principles method is used to investigate the lattice parameter, elastic constant, elastic modulus including bulk modulus （B） and shear modulus （G）, Poisson＇s ratio, and elastic anisotropy of Al, NiAl and NiaAl under extreme condition. The elastic constants obtained from calculations meet their mechanical stability criteria. Both NiAl and Ni3Al exhibit ductile behavior due to their high bulk mudulus to shear modulus ratios of B/G ratios. Through the full-electronic quasi-harmonic approximation, in which the mobile electrons are considered, we successfully obtain the thermo-physical properties including the thermal expansion coefficient, bulk modulus, heat capacity and entropy at simultaneously high temperatures and high pressures. The calculated quantities agree well with the available results. Some silent results are also interpreted. Several interesting features in the thermodynamic properties can also be observed.展开更多
We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. ...We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, dif- fering with the other four C^1, G2, C13 and 6＂33 constants. The Poisson＇s ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B]C44 investigations revealed that VzAIC is brittle and the brittleness decreases with pressure. Also, we found that V2A1C is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grtineisen pa- rameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.展开更多
基金V. ACKNOWLEDGEMENTS This work was supported by the National Natural Science Foundation of China （No.U1204501, No.11304141, No.11105115）. We thank Prof. Alberto Qtero-de-laRoza and his colleague for the FEQHA model （Gibbs2 code）. We also acknowledge Prof. M. A. Blanco and his co-workers for their QHD model （Gibbs code）.
文摘Atomistic modeling based on the accurate first-principles method is used to investigate the lattice parameter, elastic constant, elastic modulus including bulk modulus （B） and shear modulus （G）, Poisson＇s ratio, and elastic anisotropy of Al, NiAl and NiaAl under extreme condition. The elastic constants obtained from calculations meet their mechanical stability criteria. Both NiAl and Ni3Al exhibit ductile behavior due to their high bulk mudulus to shear modulus ratios of B/G ratios. Through the full-electronic quasi-harmonic approximation, in which the mobile electrons are considered, we successfully obtain the thermo-physical properties including the thermal expansion coefficient, bulk modulus, heat capacity and entropy at simultaneously high temperatures and high pressures. The calculated quantities agree well with the available results. Some silent results are also interpreted. Several interesting features in the thermodynamic properties can also be observed.
基金supported by the National Natural Science Foundation of China (Grant Nos.10974139,10964002,11104247 and 11176020)the Provincial Natural Science Foundation of Guizhou (Grant Nos.[2009]2066 and TZJF-2008-42)+2 种基金the Provincial Natural Science Foundation of Hainan (Grant No.110001)the Provincial Natural Science Foundation of Chong Qing(Grant No.CSTCcstc2011jja90002)the Provincial Natural Science Foundation of Zhejiang (Grant No.Y201121807)
文摘We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, dif- fering with the other four C^1, G2, C13 and 6＂33 constants. The Poisson＇s ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B]C44 investigations revealed that VzAIC is brittle and the brittleness decreases with pressure. Also, we found that V2A1C is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grtineisen pa- rameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.
