Wdowik Urszula D, Legut Dominik
Institute of Technology, Pedagogical University, PL-30-084 Cracow, Poland.
J Phys Condens Matter. 2009 Jul 8;21(27):275402. doi: 10.1088/0953-8984/21/27/275402. Epub 2009 Jun 10.
Vibrational dynamics of the MnO lattice has been studied using density functional theory combined with the direct method. Considerations have been limited to the harmonic approximation. Ab initio calculated Hellmann-Feynman forces were used to obtain density of states and the dispersion relations of phonons in the MnO crystal. Corrections for the local Coulomb interactions were applied. The Hubbard energies were varied from 1 to 7.9 eV. Increased Hubbard terms give a significant increase in the on-site force constants of cations, while the force constants on anions are affected indirectly. The density of phonon states and the dispersion curves are shifted to higher frequencies with the increasing Hubbard energies. The on-site Coulomb interactions influence mainly the optical phonon vibrations. The higher Hubbard terms lower the mean-squared vibrations of both cations and anions. The lattice contribution to the heat capacity experiences small changes upon variation of Coulomb repulsion. Results of the calculations are compared to the existing experimental data.
利用密度泛函理论结合直接方法研究了MnO晶格的振动动力学。考虑因素仅限于简谐近似。使用从头算计算的Hellmann-Feynman力来获得MnO晶体的态密度和声子色散关系。应用了局部库仑相互作用的校正。哈伯德能量在1至7.9电子伏特之间变化。增加的哈伯德项使阳离子的在位力常数显著增加，而阴离子的力常数受到间接影响。随着哈伯德能量的增加，声子态密度和色散曲线向更高频率移动。在位库仑相互作用主要影响光学声子振动。较高的哈伯德项降低了阳离子和阴离子的均方振动。在库仑排斥变化时，晶格对热容量的贡献经历微小变化。将计算结果与现有的实验数据进行了比较。
