论文标题
通过不可约的衍生物通过非谐音的声子行为：自洽扰动理论和分子动力学
Anharmonic phonon behavior via irreducible derivatives: self-consistent perturbation theory and molecular dynamics
论文作者
论文摘要
立方声子相互作用现在定期从第一原理计算出来，而四分之一的相互作用已经开始受到更多关注。鉴于这种现实的Anharmonic振动性哈密顿量，可以使用分子动力学精确测量经典的声子Green的功能，然后可以用来严格评估经典限制中自持续图的有效性范围。在这里，我们使用捆绑的不可衍生方法来有效，精确地计算Caf $ _2 $的立方和四分之一的声子相互作用，系统地在系统上纯粹是基于不可衍生物的振动汉密尔顿。非频移和线宽，我们证明，4个调子日落图对超过$ t = 500 $ k的光学声子线宽具有重要贡献。在使用4个弹奏循环图和评估3-phonon bubble和4-cons的自我抗性时，即使在$ t = 900 $ k中获得合理的结果，甚至在$ t = 900 $ k中获得了贡献。通过进行准粒子扰动理论获得进一步的改进，在自稳定性期间，使用4个phonon循环和3个phonon气泡的实际部分。我们对自洽扰动理论的不可还原衍生方法是研究量子和经典制度中的非谐声子的强大工具。
Cubic phonon interactions are now regularly computed from first principles, and the quartic interactions have begun to receive more attention. Given this realistic anharmonic vibrational Hamiltonian, the classical phonon Green's function can be precisely measured using molecular dynamics, which can then be used to rigorously assess the range of validity for self-consistent diagrammatic approaches in the classical limit. Here we use the bundled irreducible derivative approach to efficiently and precisely compute the cubic and quartic phonon interactions of CaF$_2$, systematically obtaining the vibrational Hamiltonian purely in terms of irreducible derivatives. non frequency shifts and linewidths, We demonstrate that the 4-phonon sunset diagram has an important contribution to the optical phonon linewidths beyond $T=500$ K. Reasonable results are obtained even at $T=900$ K when performing self-consistency using the 4-phonon loop diagram and evaluating the 3-phonon bubble and 4-phonon sunset diagrams post self-consistency. Further improvements are obtained by performing quasiparticle perturbation theory, where both the 4-phonon loop and the real part of the 3-phonon bubble are employed during self-consistency. Our irreducible derivative approach to self-consistent perturbation theory is a robust tool for studying anharmonic phonons in both the quantum and classical regimes.
