Poltavsky Igor, Kapil Venkat, Ceriotti Michele, Kim Kwang S, Tkatchenko Alexandre
Physics and Materials Science Research Unit , University of Luxembourg , L-1511 Luxembourg City , Luxembourg.
Laboratory of Computational Science and Modelling, Institute of Materials , Ecole Polytechnique Fédérale de Lausanne , Lausanne , Switzerland.
J Chem Theory Comput. 2020 Feb 11;16(2):1128-1135. doi: 10.1021/acs.jctc.9b00881. Epub 2020 Jan 22.
Imaginary time path-integral (PI) simulations that account for nuclear quantum effects (NQE) beyond the harmonic approximation are increasingly employed together with modern electronic-structure calculations. Existing PI methods are applicable to molecules, liquids, and solids; however, the computational cost of such simulations increases dramatically with decreasing temperature. To address this challenge, here, we propose to combine high-order PI factorization with perturbation theory (PT). Already for conventional second-order PI simulations, the PT ansatz increases the accuracy 2-fold compared to fourth-order schemes with the same settings. In turn, applying PT to high-order path integrals (HOPI) further improves the efficiency of simulations for molecular and condensed matter systems especially at low temperatures. We present results for bulk liquid water, the aspirin molecule, and the CH molecule. Perturbed HOPI simulations remain both efficient and accurate down to 20 K and provide a convenient method to estimate the convergence of quantum-mechanical observables.
考虑超越简谐近似的核量子效应（NQE）的虚时路径积分（PI）模拟越来越多地与现代电子结构计算一起使用。现有的PI方法适用于分子、液体和固体；然而，这种模拟的计算成本会随着温度降低而急剧增加。为应对这一挑战，我们在此提出将高阶PI因式分解与微扰理论（PT）相结合。对于传统的二阶PI模拟，与相同设置的四阶方案相比，PT假设可将精度提高两倍。反过来，将PT应用于高阶路径积分（HOPI）可进一步提高分子和凝聚态系统模拟的效率，尤其是在低温下。我们给出了体相液态水、阿司匹林分子和CH分子的结果。微扰HOPI模拟在低至20 K时仍保持高效和准确，并提供了一种方便的方法来估计量子力学可观测量的收敛性。
