Elastic constants of NaBH4 and LiBH4: Instability of -LiBH4Xiao-Dong Zhang1, Zhu-Feng Hou2, Zhen-Yi Jiang1 and Yu-Qing Hou3
1 Institute of Modern Physics, Northwest University - Xian 710069, PRC
2 Department of Physics, Fudan University - Shanghai 200433, PRC
3 Department of Electronic Science, Northwest University - Xian 710069, PRC
received 16 September 2009; accepted in final form 19 October 2009; published November 2009
published online 17 November 2009
The structural properties and mechanical stabilities of -NaBH4 and -LiBH4 have been investigated using first-principles calculations. Elastic constants of -NaBH4 and -LiBH4 are calculated from the second derivative of total energy as a function of strain. The calculated structural parameters and elastic constants of -NaBH4 are in good agreement with the available experimental data. Our calculations show that -LiBH4 with P63mc space group is unstable under the distortions (0, 0, 0, , , 0) and (0, 0, 0, 0, 0, ) and these distortions lead to a Martensitic transformation into Cc and Cmc21 structures, respectively. Thermodynamically, -LiBH4 with P63mc space group is more likely changed into a Cmc21 structure, which is consistent with experimental results.
62.20.D- - Elasticity.
81.30.Kf - Martensitic transformations.
© EPLA 2009