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首页> 外文期刊>The Journal of Chemical Physics >Efficient and accurate approximations to the local coupled cluster singlesdoubles method using a truncated pair natural orbital basis
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Efficient and accurate approximations to the local coupled cluster singlesdoubles method using a truncated pair natural orbital basis

机译：使用截短对自然轨道基础对局部耦合簇Singlesdoubles方法进行有效且精确的近似

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摘要

A production level implementation of the closed-shell local quadratic configuration interaction andcoupled cluster methods with single and double excitations (QCISD and CCSD) based on theconcept of pair natural orbitals [local pair natural orbital LPNO-QCISD and LPNO-CCSD) isreported, evaluated, and discussed. This work is an extension of the earlier developed LPNOcoupled-electron pair approximation (LNPO-CEPA) method [F. Neese et al., Chem. Phys. 130,114108 (2009)] and makes extended use of the resolution of the identity (RI) or density fitting (DF)approximation. Two variants of each method are compared. The less accurate approximations(LPNO_2-QCISD/LPNO_CCSD) still recover 98.7%-99.3% of the correlation energy in givenbasis and have modest disk space requirements. The more accurate variants(LPNO_1-QCISD/LPNO_CCSD) typically recover 99.75%-99.95% of the correlation energy in thegiven basis but require the Coulomb and exchange operators with up to two-external indices to bestored on disk. Both variants have comparable computational efficiency. The convergence of theresults with respect to the natural orbital truncation parameter (T_(CutPNO))has been studied. Extendednumerical tests have been performed on absolute and relative correlation energies as function ofbasis set size and T_(CutPNO)as well on reaction energies, isomerization and weakintermolecular interactions. The results indicate that the errors of the LPNO methods compared tothe canonical QCISD and CCSD methods are below 1 kcal/mol with our default thresholds. Finally,some calculations on larger molecules are reported (ranging from 40-86 atoms) and it is shown thatfor medium sized molecules the total wall clock time required to complete the LPNO-CCSDcalculations is only two to four times that of the preceding self-consistent field (SCF). Thus thesemethods are highly suitable for large-scale computational chemistry applications. Since there areonly three thresholds involved that have been given conservative default values, the methods can beconfidentially used in a black-box fashion in the same way as their canonical counterparts.
机译：报告，评估，评估了基于成对自然轨道[局部成对自然轨道LPNO-QCISD和LPNO-CCSD]概念的单壳和双激发（QCISD和CCSD）闭壳局部二次配置相互作用和耦合聚类方法的生产水平实现，和讨论。这项工作是对较早开发的LPNO耦合电子对近似（LNPO-CEPA）方法的扩展[F. Neese等，化学。物理130,114108（2009）]，并广泛使用了同一性（RI）或密度拟合（DF）近似值的分辨率。比较每种方法的两个变体。精度较低的近似值（LPNO_2-QCISD / LPNO_CCSD）在给定的基础上仍可恢复98.7％-99.3％的相关能量，并且磁盘空间要求适中。在给定的基础上，更准确的变体（LPNO_1-QCISD / LPNO_CCSD）通常可以恢复99.75％-99.95％的相关能量，但需要库仑和交换操作员将最多两个外部索引存储在磁盘上。两种变体都具有可比的计算效率。研究了关于自然轨道截断参数（T_（CutPNO））的结果的收敛性。已经对绝对和相对相关能量作为基础集大小和T_（CutPNO）的函数进行了扩展的数值测试，还对反应能量，异构化和弱分子间相互作用进行了测试。结果表明，与我们的默认阈值相比，与常规QCISD和CCSD方法相比，LPNO方法的误差低于1 kcal / mol。最后，据报道对较大分子进行了一些计算（范围为40-86个原子），结果表明，对于中等大小的分子，完成LPNO-CCSD计算所需的总挂钟时间仅是以前的自洽计算的2-4倍。字段（SCF）。因此，这些方法非常适合大规模计算化学应用。由于仅涉及三个阈值，并已为其提供了保守的默认值，因此可以以黑盒的方式以机密方式使用这些方法，就像使用其对应的标准方法一样。

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