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首页> 外文期刊>Computer physics communications >PHON: A program to calculate phonons using the small displacement method
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PHON: A program to calculate phonons using the small displacement method

机译：PHON：使用小位移法计算声子的程序

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摘要

The program PHON calculates force constant matrices and phonon frequencies in crystals. From the frequencies it also calculates various thermodynamic quantities, like the Helmholtz free energy, the entropy, the specific heat and the internal energy of the harmonic crystal. The procedure is based on the small displacement method, and can be used in combination with any program capable to calculate forces on the atoms of the crystal. In order to examine the usability of the method, I present here two examples: metallic Al and insulating MgO. The phonons of these two materials are calculated using density functional theory. The small displacement method results are compared with those obtained using the linear response method. In the case of Al the method provides accurate phonon frequencies everywhere in the Brillouin Zone (BZ). In the case of MgO the longitudinal branch of the optical phonons near the centre of the BZ is incorrectly described as degenerate with the two transverse branches, because the non-analytical part of the dynamical matrix is ignored here; however. thermodynamic properties like the Helmholtz free are essentially unaffected.
机译：PHON程序可计算晶体中的力常数矩阵和声子频率。从频率还可以计算出各种热力学量，例如亥姆霍兹自由能，熵，比热和谐波晶体的内能。该程序基于小位移法，可与能够计算晶体原子力的任何程序结合使用。为了检查该方法的可用性，我在这里提供两个示例：金属Al和绝缘MgO。这两种材料的声子是使用密度泛函理论计算的。将小位移法结果与使用线性响应法获得的结果进行比较。在铝的情况下，该方法可在布里渊区（BZ）的任何地方提供准确的声子频率。在MgO的情况下，BZ中心附近的光子的纵向声子被错误地描述为由两个横向分支退化，因为动力学矩阵的非分析部分在这里被忽略了。然而。诸如不含亥姆霍兹的热力学性质基本上不受影响。

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