论文标题
使用半矛盾的热浴配置相互作用方法的高斯-2几乎精确的能量
Almost exact energies for the Gaussian-2 set with the semistochastic heat-bath configuration interaction method
论文作者
论文摘要
最近开发的半伴随热浴配置相互作用（SHCI）方法是一种系统地改进的选择配置相互作用加上扰动理论方法，能够为更大的系统提供基本精确的能量，而不是其他此类方法。我们计算了55个分子的SHCI雾化能，这些分子已在先前的研究中用作测试集，因为它们的雾化能是从实验中知道的。使用了从CC-PVDZ到CC-PV5Z的基集，总计多达500个轨道，Hilbert空间为$ 10^{32} $ Slater决定因素，用于最大的分子。对于每个基础，在化学精度（1 kcal/mol或1.6 mha/mol）中，精确的能量在该基础上仅使用整个希尔伯特空间的一小部分来计算。我们还使用几乎精确的能量来基准耦合群集[CCSD（t）]能量。将能量外推到完整的基集限制，并与实验雾化能。外推是基于密度功能理论的基础校正和基础校正的。这些外推实验的平均绝对偏差分别为0.46 kcal/mol和0.51 kcal/mol。还讨论了用于获得改善SHCI能量收敛性的轨道优化方法。
The recently developed semistochastic heat-bath configuration interaction (SHCI) method is a systematically improvable selected configuration interaction plus perturbation theory method capable of giving essentially exact energies for larger systems than is possible with other such methods. We compute SHCI atomization energies for 55 molecules which have been used as a test set in prior studies because their atomization energies are known from experiment. Basis sets from cc-pVDZ to cc-pV5Z are used, totaling up to 500 orbitals and a Hilbert space of $10^{32}$ Slater determinants for the largest molecules. For each basis, an extrapolated energy well within chemical accuracy (1 kcal/mol or 1.6 mHa/mol) of the exact energy for that basis is computed using only a tiny fraction of the entire Hilbert space. We also use our almost exact energies to benchmark coupled-cluster [CCSD(T)] energies. The energies are extrapolated to the complete basis set limit and compared to the experimental atomization energies. The extrapolations are done both without and with a basis-set correction based on density-functional theory. The mean absolute deviations from experiment for these extrapolations are 0.46 kcal/mol and 0.51 kcal/mol, respectively. Orbital optimization methods used to obtain improved convergence of the SHCI energies are also discussed.
