论文标题
无多体密度失真的分散体：原子和小分子的评估
Dispersion without many-body density distortion: Assessment on atoms and small molecules
论文作者
论文摘要
我们已经实施并测试了我们最近提出的方法[J。物理。化学Lett。 10，1537（2019）]处理分散相互作用，该相互作用源自限制的超分子波函数，以使每个单体的多体密度基质的对角线保持不变。相应的变分优化可导致分散系数的表达式，仅在隔离单体的地面对密度方面，这提供了一个框架来构建新的近似值，而无需极化或虚拟轨道。我们要在这里回答的问题是，在使用来自不同理论的不同级别的单体对密度时，即Hartree-Fock，MP2和CCSD时，我们的各向同性和各向异性$ C_6 $分散系数都可以适用于各向同性和各向异性$ C_6 $分散系数。对于封闭系统，具有CCSD单体对密度的FDM可产生最佳结果，以及各向同性$ C_6 $分散系数的平均百分比误差约为7 \％，并且在18 \％以内的最大绝对误差。发现在CCSD接地状态顶部具有FDM的各向异性分散系数的准确性。开放壳系统的性能不那么令人满意，CCSD对密度并不总是提供最佳结果。在目前的实现中，单体基本计算的计算成本为$ \ MATHCAL {O}（n^4）$。
We have implemented and tested the method we have recently proposed [J. Phys. Chem. Lett. 10, 1537 (2019)] to treat dispersion interactions, which is derived from a supramolecular wavefunction constrained to leave the diagonal of the many-body density matrix of each monomer unchanged. The corresponding variational optimization leads to expressions for the dispersion coefficients in terms of the ground-state pair densities of the isolated monomers only, which provides a framework to build new approximations without the need for polarizabilities or virtual orbitals. The question we want to answer here is how accurate this ``fixed diagonal matrices'' (FDM) method can be for isotropic and anisotropic $C_6$ dispersion coefficients when using monomer pair densities from different levels of theory, namely Hartree-Fock, MP2 and CCSD. For closed-shell systems, FDM with CCSD monomer pair densities yields the best results, with a mean average percent error for isotropic $C_6$ dispersion coefficients of about 7\% and a maximum absolute error within 18\%. The accuracy for anisotropic dispersion coefficients with FDM on top of CCSD ground states is found to be similar. The performance for open shell systems is less satisfactory, with CCSD pair densities not always providing the best result. In the present implementation, the computational cost on top of the monomer's ground-state calculations is $\mathcal{O}(N^4)$.
