Mellouki A, Bennecer B, Kalarasse F
Physics Laboratory at Guelma, Faculty of Science and Engineering, University of Guelma, PO Box 401, Guelma 24000, Algeria.
J Phys Condens Matter. 2009 Jul 29;21(30):305402. doi: 10.1088/0953-8984/21/30/305402. Epub 2009 Jul 8.
We have studied the vibrational properties of the filled tetrahedral semiconductor LiMgAs and its binary analog AlAs by using the plane-wave pseudopotential method within density functional theory. The calculated lattice constants for the studied compounds are in good agreement with previous theoretical and experimental results. The phonon dispersion curves and phonon density of states are calculated by using density functional perturbation theory. The sound speeds in different directions are quantitatively similar in LiMgAs and AlAs. The assignment of the zone center modes to the relative motion of the atoms shows that the lower optic modes are due to the Mg-As pair vibrations, while for the upper ones the Li-Mg pair dominates, which is attributed to the smaller Mg atom mass. The longitudinal interatomic force constant of Mg-As is about 66% higher than that of Li-As, showing the relatively high covalency of the former bond.
我们采用密度泛函理论中的平面波赝势方法，研究了填充四面体半导体LiMgAs及其二元类似物AlAs的振动特性。所研究化合物的计算晶格常数与先前的理论和实验结果吻合良好。利用密度泛函微扰理论计算了声子色散曲线和声子态密度。LiMgAs和AlAs中不同方向的声速在数量上相似。将区中心模式分配给原子的相对运动表明，较低的光学模式归因于Mg-As对的振动，而对于较高的光学模式，Li-Mg对起主导作用，这归因于Mg原子质量较小。Mg-As的纵向原子间力常数比Li-As的约高66%，表明前者键的共价性相对较高。
