Wiberg Kenneth B, Wang Yi-gui, de Oliveira Anselmo E, Perera S Ajith, Vaccaro Patrick H
Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA.
J Phys Chem A. 2005 Jan 27;109(3):466-77. doi: 10.1021/jp040558j.
The CIS and EOM-CCSD adiabatic geometries for the first excited states of a set of small molecules (C2H4, C2H2, H2C=O, H2C=S, CS2, CO2, SO2, NO2) have been calculated using the 6-311++G** basis set to see if the former geometries can be good starting points for optimizations at the latter theoretical level. With most of the molecules, there is fairly good agreement between the results from the two methods, and EOM-CCSD gives good agreement with the available experimental data. A detailed discussion of the lowest-lying singlet excited states in CO2 and CS2 is presented, highlighting the pronounced differences in electronic character and equilibrium structure displayed by these isovalent species. The origins of the structural distortions that are frequently found for the adiabatic excited states are examined with the aid of deformation density plots and the electron localization function (ELF).
已使用6-311++G**基组计算了一组小分子（C2H4、C2H2、H2C=O、H2C=S、CS2、CO2、SO2、NO2）第一激发态的CIS和EOM-CCSD绝热几何结构，以查看前一种几何结构是否可以作为后一种理论水平优化的良好起点。对于大多数分子，两种方法的结果之间有相当好的一致性，并且EOM-CCSD与现有的实验数据吻合良好。本文对CO2和CS2中最低的单重激发态进行了详细讨论，突出了这些等电子物种在电子特性和平衡结构上的显著差异。借助变形密度图和电子定域函数（ELF）研究了绝热激发态中经常出现的结构畸变的起源。
