Accurate first-derivative nonadiabatic couplings for the H3 system
Accurate first-derivative nonadiabatic couplings for the H3 system
复制标题
H3 系统的精确一阶导数非绝热耦合
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
D. Yarkony
中科院分区：
文献类型：
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作者：
R. Abrol;Amy Shaw;A. Kuppermann;D. Yarkony
C3v几何构型的H3系统的基态（1 2A）和第一激发态（2 2A）电子势能面（PES）之间存在一个圆锥相交。这种交叉诱导的几何相位效应，一个重要的因素，在准确的量子力学反应散射计算，这在低能量下可以使用地面PES只，连同适当的核运动边界条件。然而，在更高的能量下，这样的计算需要包括1 2A[prime]和2 2A[prime]电子PES和相应的核导数耦合。在这里，我们提出了从头算一阶导数耦合这些状态得到的解析梯度技术和适合这些结果。我们还提出了一个适合于相应的1 2A[素数]和2 2A[素数]绝热电子PES，从从头算电子能量。将一阶导数偶合与Varandas等人[J. Chem. Phys. 86，6258（1987）]用双多体展开法得到的近似解析偶合进行了比较。正如预期的那样，后者是准确的接近圆锥形交叉配置，但不是其他地方。我们还给出了从头算耦合沿着上述圆锥相交处的闭合环的围道积分，它包含了2个2A[prime]态和3个2A[prime]态之间可能相互作用的信息.
A conical intersection exists between the ground (1 2 A[prime]) and the first-excited (2 2A[prime]) electronic potential energy surfaces (PESs) of the H3 system for C3v geometries. This intersection induces a geometric phase effect, an important factor in accurate quantum mechanical reactive scattering calculations, which at low energies can be performed using the ground PES only, together with appropriate nuclear motion boundary conditions. At higher energies, however, such calculations require the inclusion of both the 1 2A[prime] and 2 2A[prime] electronic PESs and the corresponding nuclear derivative couplings. Here we present ab initio first-derivative couplings for these states obtained by analytic gradient techniques and a fit to these results. We also present a fit to the corresponding 1 2A[prime] and 2 2A[prime] adiabatic electronic PESs, obtained from the ab initio electronic energies. The first-derivative couplings are compared with their approximate analytical counterparts obtained by Varandas et al. [J. Chem. Phys. 86, 6258 (1987)] using the double many-body expansion method. As expected, the latter are accurate close to conical intersection configurations but not elsewhere. We also present the contour integrals of the ab initio couplings along closed loops around the above-mentioned conical intersection, which contain information about possible interactions between the 2 2A[prime] and 3 2A[prime] states.