Lee Joonho, Morales Miguel A, Malone Fionn D
Department of Chemistry, Columbia University, New York, New York 10027, USA.
Quantum Simulations Group, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94551, USA.
J Chem Phys. 2021 Feb 14;154(6):064109. doi: 10.1063/5.0041378.
We investigate the viability of the phaseless finite-temperature auxiliary-field quantum Monte Carlo (ph-FT-AFQMC) method for ab initio systems using the uniform electron gas as a model. Through comparisons with exact results and FT coupled cluster theory, we find that ph-FT-AFQMC is sufficiently accurate at high to intermediate electronic densities. We show, both analytically and numerically, that the phaseless constraint at FT is fundamentally different from its zero-temperature counterpart (i.e., ph-ZT-AFQMC), and generally, one should not expect ph-FT-AFQMC to agree with ph-ZT-AFQMC in the low-temperature limit. With an efficient implementation, we are able to compare exchange-correlation energies to the existing results in the thermodynamic limit and find that the existing parameterizations are highly accurate. In particular, we found that ph-FT-AFQMC exchange-correlation energies are in better agreement with a known parameterization than is restricted path-integral MC in the regime of Θ ≤ 0.5 and r ≤ 2, which highlights the strength of ph-FT-AFQMC.
我们以均匀电子气为模型，研究了无相位有限温度辅助场量子蒙特卡罗（ph-FT-AFQMC）方法用于从头算系统的可行性。通过与精确结果和有限温度耦合簇理论进行比较，我们发现ph-FT-AFQMC在高至中等电子密度下具有足够的准确性。我们通过解析和数值方法表明，有限温度下的无相位约束与其零温度对应物（即ph-ZT-AFQMC）有根本不同，一般来说，不应期望ph-FT-AFQMC在低温极限下与ph-ZT-AFQMC一致。通过高效的实现方式，我们能够将交换关联能与热力学极限下的现有结果进行比较，并发现现有参数化非常准确。特别是，我们发现，在Θ≤0.5和r≤2的范围内，ph-FT-AFQMC交换关联能与已知参数化的一致性比受限路径积分蒙特卡罗更好，这突出了ph-FT-AFQMC的优势。
