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基于密度泛函微扰理论(DFPT)结合模守恒赝势方法进行晶格动力学模拟.得到了钇铝石榴石(YAG)的声子态密度、分波声子态密度和声子的色散谱.利用第一Brillouin区的特殊点取样方法,计算了YAG的比热容和布局数平均的声子群速度.在非谐相互作用下,利用Fermi黄金公式结合第一Brillouin区的特殊点取样方法,得出了YAG非谐声子平均自由程.综合考虑了两种声子散射机制,得到了YAG陶瓷的热导率.结果表明,对于YAG陶瓷,在低温时,晶界散射将对热阻起主要作用;在高于一定温度时,三声子相互作用对热阻的贡献将占主导地位.同时也从理论上证明了Sato等提出的在室温以上,YAG陶瓷与单晶的热导率的差异可以忽略的观点.所得到的热导率、比热容随温度的变化与实验结果很好地符合.
Lattice dynamics simulation was performed based on DFPT combined with mode-locked pseudopotential. The phonon density, the phonon density and the phonon dispersion spectrum of yttrium aluminum garnet (YAG) were obtained. Using the special sampling method of Brillouin zone, the specific heat capacity of YAG and the average phonon population velocity are calculated.Under the condition of anharmonic interaction, using the Fermi gold formula combined with the special sampling method of the first Brillouin zone, The mean free path of the YAG inhomogeneous phonon is obtained.The thermal conductivities of YAG ceramics are obtained by considering two phonon scattering mechanisms.The results show that the grain boundary scattering plays a major role in the thermal resistance of YAG ceramics at low temperature ; At above a certain temperature, the contribution of the three-phonon interaction to the thermal resistance will dominate. At the same time, it is also theoretically proved that the difference between the thermal conductivities of YAG ceramics and single crystals proposed by Sato et al. Neglected point of view.The resulting thermal conductivity, specific heat capacity with temperature changes and experimental results in good agreement.