Mahajan Ankit, Lee Joonho, Sharma Sandeep
Department of Chemistry, University of Colorado, Boulder, Colorado 80302, USA.
Department of Chemistry, Columbia University, New York, New York 10027, USA.
J Chem Phys. 2022 May 7;156(17):174111. doi: 10.1063/5.0087047.
We present efficient algorithms for using selected configuration interaction (sCI) trial wave functions in phaseless auxiliary field quantum Monte Carlo (ph-AFQMC). These advances, geared toward optimizing computational performance for longer configuration interaction expansions, allow us to use up to a million configurations in the trial state for ph-AFQMC. In one example, we found the cost of ph-AFQMC per sample to increase only by a factor of about 3 for a calculation with 10 configurations compared to that with a single one, demonstrating the tiny computational overhead due to a longer expansion. This favorable scaling allows us to study the systematic convergence of the phaseless bias in auxiliary field quantum Monte Carlo calculations with an increasing number of configurations and provides a means to gauge the accuracy of ph-AFQMC with other trial states. We also show how the scalability issues of sCI trial states for large system sizes could be mitigated by restricting them to a moderately sized orbital active space and leveraging the near-cancellation of out of active space phaseless errors.
我们提出了在无相辅助场量子蒙特卡罗（ph-AFQMC）中使用选定组态相互作用（sCI）试探波函数的高效算法。这些进展旨在优化更长组态相互作用展开的计算性能，使我们能够在ph-AFQMC的试探态中使用多达一百万个组态。在一个例子中，我们发现与使用单个组态的计算相比，对于具有10个组态的计算，ph-AFQMC每个样本的成本仅增加约3倍，这表明由于更长的展开导致的计算开销极小。这种有利的缩放比例使我们能够研究辅助场量子蒙特卡罗计算中无相偏差随着组态数量增加的系统收敛情况，并提供了一种用其他试探态来衡量ph-AFQMC准确性的方法。我们还展示了如何通过将sCI试探态限制在适度大小的轨道活性空间，并利用活性空间外无相误差的近抵消来缓解大系统尺寸下sCI试探态的可扩展性问题。
