Banik Subrata, Ravichandran Lalitha, Brabec Jiří, Hubač Ivan, Kowalski Karol, Pittner Jiří
J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic.
Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
J Chem Phys. 2015 Mar 21;142(11):114106. doi: 10.1063/1.4914311.
As a further development of the previously introduced a posteriori Universal State-Selective (USS) corrections [K. Kowalski, J. Chem. Phys. 134, 194107 (2011); J. Brabec et al., ibid. 136, 124102 (2012)], we suggest an iterative form of the USS correction by means of correcting effective Hamiltonian matrix elements. We also formulate USS corrections via the left Bloch equations. The convergence of the USS corrections with excitation level towards the full configuration interaction (FCI) limit is also investigated. Various forms of the USS and simplified diagonal USS corrections at the singles and doubles and perturbative triple levels are numerically assessed on several model systems and on the ozone and tetramethyleneethane molecules. It is shown that the iterative USS correction can successfully replace the previously developed a posteriori Brillouin-Wigner coupled cluster size-extensivity correction, while it is not sensitive to intruder states and performs well also in other cases when the a posteriori one fails, like, e.g., for the asymmetric vibration mode of ozone.
作为对先前引入的后验通用态选择（USS）校正[K. Kowalski，《化学物理杂志》134，194107（2011）；J. Brabec等人，同上，136，124102（2012）]的进一步发展，我们通过校正有效哈密顿矩阵元提出了一种USS校正的迭代形式。我们还通过左布洛赫方程来制定USS校正。同时研究了USS校正在激发能级上向完全组态相互作用（FCI）极限的收敛情况。在几个模型系统以及臭氧和四亚甲基乙烷分子上，对单双激发和微扰三重激发水平下的各种形式的USS以及简化的对角USS校正进行了数值评估。结果表明，迭代USS校正能够成功取代先前开发的后验布里渊 - 维格纳耦合簇尺寸扩展性校正，它对侵入态不敏感，并且在其他后验校正失败的情况下（例如臭氧的不对称振动模式）也表现良好。
