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Ab initio study of phase transition and bulk modulus of NaH |
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| Authors: | Xiao-Wei Sun Qi-Feng Chen Xiang-Rong Chen Ling-Cang Cai |
| Institution: | a Institute of Atomic and Molecular Physics, School of Physical Science and Technology, Sichuan University, Chengdu 610065, PR China b National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, PR China c School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070, PR China d International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, PR China |
| Abstract: | The phase transition of NaH from NaCl- to CsCl-type structure is investigated by an ab initio plane-wave pseudopotential density functional theory method with the norm-conserving pseudopotential scheme in the frame of the generalized gradient approximation correction; the isothermal bulk modulus and its first and second pressure derivatives of the NaCl- and CsCl-type structures under high pressure and temperature are obtained through the quasi-harmonic Debye model. The phase transition obtained from the usual condition of equal enthalpies occurs at the pressure of 32 GPa, which is consistent with the experimental and other calculated values. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of cell volume V and lattice constant a on temperature T at zero pressure, the isothermal bulk modulus B0 and its pressure derivatives B0′and B0″ on pressure P along isotherms 0, 300, and 600 K, are also successfully obtained. |
| Keywords: | NaH Phase transition Bulk modulus High pressure |
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