Toboła R, Chałasiński G, Kłos J, Szcześniak M M
Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
J Chem Phys. 2009 May 14;130(18):184304. doi: 10.1063/1.3123168.
This study reports an ab initio characterization of a prereactive van der Waals complex between an open-shell atom Br((2)P) and a closed shell molecule HBr. The three adiabatic potential surfaces 1 (2)A('), 2 (2)A('), and 1 (2)A("), which result from the splitting of degenerate P state of Br are obtained from coupled cluster calculations. The coupling between same-symmetry states is calculated by multireference configuration-interaction method. A transformation to a diabatic representation and inclusion of the spin-orbit coupling effects on the interactions are also discussed. Bound states are calculated using an adiabatic bender model. The global minimum on the lowest adiabatic potential surface corresponds to a T-shaped geometry and has a well depth of D(e)=762.5 cm(-1) at R(e)=3.22 A. A secondary minimum occurs for a hydrogen-bonded geometry with D(e)=445.3 cm(-1) at R(e)=4.24 A. Upon inclusion of spin-orbit coupling the hydrogen-bonded minimum remains at the same depth, but the T-shaped minimum washes out to less than half of its spin-free value. The lowest bound state is localized in the linear minimum. The spin-orbit coupling plays a very important role in shaping of the potential energy surfaces of Br-HBr.
本研究报告了对开壳层原子Br((2)P)与闭壳层分子HBr之间预反应范德华复合物的从头算表征。通过耦合簇计算获得了由Br的简并P态分裂产生的三个绝热势能面1 (2)A(')、2 (2)A(')和1 (2)A(")。利用多参考组态相互作用方法计算了同对称态之间的耦合。还讨论了向 diabatic 表象的变换以及自旋轨道耦合效应在相互作用中的包含情况。使用绝热弯曲模型计算束缚态。最低绝热势能面上的全局最小值对应于T形几何结构，在R(e)=3.22 Å时阱深为D(e)=762.5 cm(-1)。对于氢键几何结构，在R(e)=4.24 Å时出现二级最小值，D(e)=445.3 cm(-1)。包含自旋轨道耦合后，氢键最小值保持在相同深度，但T形最小值消失至其无自旋值的一半以下。最低束缚态定域在线性最小值处。自旋轨道耦合在Br-HBr势能面的形成中起着非常重要的作用。
