Extrapolating to the one-electron basis-set limit in electronic structure calculations.
Extrapolating to the one-electron basis-set limit in electronic structure calculations.
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DOI：
10.1063/1.2741259
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发表时间：
2007-06
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通讯作者：
A. Varandas
中科院分区：
文献类型：
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作者：
A. Varandas
一个简单的，但可靠的，计划的基础上处理均匀的单重态对和三重态对相互作用的建议外推原子和分子的电子相关能计算在两个基础上从头算理论的无限单电子基组限制。新的双水平方法首先在外推单参考耦合簇单能量和双能量的闭合壳层系统CH 2（（1）A1），H2O，HF，N2，CO，Ne和F2上进行测试，其中相关一致基组为Klopper报道的类型cc-pVXZ（X = D，T，Q，5，6）。Phys.6，481（2001）]与他自己的基准计算结果进行了比较，该基准计算使用了从显式相关的单双耦合簇理论获得的大的非收缩基组。比较也报告了相同的数据集，但使用单参考Moller-Plesset和耦合簇双打方法。结果显示出类似的，往往更好，符合目标结果比Klopper的外推，单对和三重态对能量分别外推使用流行的X（-3）和X（-5）双能级定律，分别。本文对He，H_2，HeH~+，He_2~++，H_3~+（1（1）A ′），H_3~+（1（3）A ′），BH，CH，NH，OH，FH，B_2，C_2，N_2，O_2，F_2，BO，CO，NO，BN，CN，SH，H_2O，H_3~+（1（3）A ′），B_2，C_2，N_2，O_2，F_2，BO，CO，NO，CN，H_2O，H_3~+（1（1）A ′），H_3~+（1（3）A ′），B_2，CH，NH，OH，FH，B_2，C_2，N_2，O_2，F_2，BO，CO，NO，BN，CN，SH，H_2O，H_3~+（1（1）A ′），H_3~+（1（3）A ′），H_3和NH_3在aug-cc-pVXZ（X = D，T，Q，5，6）型标准增广相关一致基组下的计算结果。尽管缺乏准确的理论或实验数据进行比较，在大多数双原子系统的情况下，新的方法也显示在这种情况下，从传统的方案，使用两个最大的负担得起的基组外推得到的结果判断时，表现出良好的性能。对于Hartree-Fock和完全活跃的空间自洽场能量，一个简单的实用外推规则进行检查，其结果被证明是比较以及从最好的报告计划获得的。
A simple, yet reliable, scheme based on treating uniformly singlet-pair and triplet-pair interactions is suggested to extrapolate atomic and molecular electron correlation energies calculated at two basis-set levels of ab initio theory to the infinite one-electron basis-set limit. The novel dual-level method is first tested on extrapolating the full correlation in single-reference coupled-cluster singles and doubles energies for the closed-shell systems CH2((1)A1), H2O, HF, N2, CO, Ne, and F2 with correlation-consistent basis sets of the type cc-pVXZ (X=D,T,Q,5,6) reported by Klopper [Mol. Phys. 6, 481 (2001)] against his own benchmark calculations with large uncontracted basis sets obtained from explicit correlated singles and doubles coupled-cluster theory. Comparisons are also reported for the same data set but using both single-reference Moller-Plesset and coupled-cluster doubles methods. The results show a similar, often better, accordance with the target results than Klopper's extrapolations where singlet-pair and triplet-pair energies are extrapolated separately using the popular X(-3) and X(-5) dual-level laws, respectively. Applications to the extrapolation of the dynamical correlation in multireference configuration interaction calculations carried out anew for He, H2, HeH+, He2 ++, H3+(1 (1)A'), H3+(1 (3)A'), BH, CH, NH, OH, FH, B2, C2, N2, O2, F2, BO, CO, NO, BN, CN, SH, H2O, and NH3 with standard augmented correlation-consistent basis sets of the type aug-cc-pVXZ (X=D,T,Q,5,6) are also reported. Despite lacking accurate theoretical or experimental data for comparison in the case of most diatomic systems, the new method also shows in this case a good performance when judged from the results obtained with the traditional schemes which extrapolate using the two largest affordable basis sets. For the Hartree-Fock and complete-active space self-consistent field energies, a simple pragmatic extrapolation rule is examined whose results are shown to compare well with the ones obtained from the best reported schemes.