Li-N-H储氢体系热力学性质的第一性原理研究

Thermodynamic properties of Li-N-H hydrogen storage: first-principles study

基于密度泛函理论的第一性原理方法,系统地研究了Li-N-H储氢过程中各个化合物的晶胞参数、生成焓和化学反应焓.结果发现优化后的晶格参数与先前的理论和实验研究符合得很好.通过计算Li3N,LiH,LiNH2和Li2NH在298K的生成焓分别为168.7,81.0,173.0和190.8kJ/mol,进而计算得到整个储氢反应过程在T=298K时反应焓为78.5kJ/molH2,这和他人计算得到T=300K的结果75.67kJ/molH2非常接近.最后,给出了储氢两步反应过程分别在T=298K时的反应焓,这些结果都与实验和他人理论计算得到的数据符合较好.

According to the plane wave pseudo-potential method of the first-principles based on density functional theory, we systematically investigate the cell parameters, the formation heat and the reaction enthalpy in the Li-N-H hydrogen storage process. The calculated lattice parameters of these compounds are in good agreement with previous theoretical and experimental results. The values of formation heat at 298 K for （lithium nitride） Li3N, （lithium hydride） LiH, （lithium amide） LiNH2 and （lithium imide） Li2NH are estimated to be 168.7, 81.0, 173.0 and 190.8kJ/mol, respectively. The reaction enthalpy of this system is calculated to be 78.5 kJ/mol H2 at T = 298 K and this value accords with the experimental value of 75.67 kJ/mol H2 at T = 300 K. As a result, the reaction enthalpies for the two-step reactions are very close to their calculation results respectively.