Wang Zhenling, Aldossary Abdulrahman, Shi Tianyi, Liu Yang, Li Xiaoye S, Head-Gordon Martin
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
J Chem Theory Comput. 2023 Nov 14;19(21):7577-7591. doi: 10.1021/acs.jctc.3c00744. Epub 2023 Oct 25.
It has long been clear that electron correlation methods exhibit unphysical compute scalings with molecular size, which has motivated the development of local correlation methods to discard effectively zero contributions in a controlled way to yield an approximate correlation energy. The ideal local correlation method should have a single numerical threshold that controls the dropping of terms with the ability to have that threshold set small enough so that the correlation energy is reproduced to enough significant figures such that the result is chemically identical. This work reports such a method for the second-order Møller-Plesset (MP2) theory. The theory, implementation, and testing of this local MP2 theory are reported. Thresholds ranging from 10 to 10 and basis sets ranging from split valence plus polarization through to quadruple-ζ are assessed for local MP2 calculations on a range of molecules, including linear chains and molecules with two- and three-dimensional character. The implementation is shared memory parallel via OpenMP and yields roughly 50% parallel efficiency with 16 cores for a large job. Considerable efforts were made to minimize memory demands, which increased as thresholds were tightened. A variety of relative energy calculations are presented as a function of threshold to provide some guidance to users on how to obtain adequate precision at a low compute cost. It is particularly clear that derivative properties require tighter thresholds in order to achieve an adequate precision.
长期以来，很明显电子相关方法随着分子大小呈现出不符合物理实际的计算缩放比例，这推动了局部相关方法的发展，以便以可控的方式有效舍弃近似为零的贡献，从而得到近似的相关能。理想的局部相关方法应该有一个单一的数值阈值来控制项的舍弃，并且能够将该阈值设置得足够小，使得相关能能够被精确重现，从而结果在化学上是相同的。这项工作报告了一种用于二阶莫勒-普莱塞特（MP2）理论的此类方法。报告了这种局部MP2理论的理论、实现和测试。对一系列分子（包括线性链以及具有二维和三维特征的分子）进行局部MP2计算时，评估了从10到10的阈值以及从分裂价加极化到四重ζ的基组。该实现通过OpenMP进行共享内存并行化，对于大型任务，在16个核心上产生约50%的并行效率。为了最小化内存需求付出了相当大的努力，随着阈值收紧，内存需求会增加。给出了各种相对能量计算作为阈值的函数，为用户提供一些关于如何以低计算成本获得足够精度的指导。特别明显的是，导数性质需要更严格的阈值才能达到足够的精度。
