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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Searching for Conical Intersections of Potential Energy Surfaces with the ONIOM Method:Application to Previtamin D
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Searching for Conical Intersections of Potential Energy Surfaces with the ONIOM Method:Application to Previtamin D

机译：用ONIOM方法寻找势能面的圆锥形相交点：在维生素原D中的应用

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摘要

We demonstrate that the ONIOM method can be used to optimize a conical intersection between the ground and first excited-state potential energy surfaces of previtamin D(precalciferol),with excitation localized in a small part of the molecule:the hexatriene chromophore.These calculations were up to 100 times faster with little loss of accuracy compared to a full non-ONIOM Target calculation.The most accurate ONIOM method combination was CASSCF/4-31G//ROHF/STO-3G(Triplet):in comparison to the Target(CASSCF/4-31G),bond lengths and angles in the hexatriene model region were calculated to within 0.02 A and 0.7°,respectively,and the energy difference between the conical intersection and nearest associated S1 minimum to within 0.5 kcal·mol~(-1).All of the low-level methods selected produced accurate geometries,including the UFF molecular mechanics and AMI semiempirical methods,suggesting a cheap and efficient way of initially optimizing conical intersections geometries.Furthermore,ONIOM allows for an assessment of the localization of excited states,providing some fundamental insight into the physical processes involved.
机译：我们证明了ONIOM方法可用于优化地面和维生素原D（钙化前醇）的第一激发态势能表面之间的圆锥形交点，激发分布在分子的一小部分：六三烯生色团中。与完整的非ONIOM目标计算相比，速度提高了100倍，并且几乎没有准确性损失。最准确的ONIOM方法组合是CASSCF / 4-31G // ROHF / STO-3G（Triplet）：与Target（CASSCF）相比/ 4-31G），六边形模型区域中的键长和键角分别计算在0.02 A和0.7°之内，并且圆锥形交点与最近的相关S1之间的能量差最小值在0.5 kcal·mol〜（-1）之内）。选择的所有低层方法都产生了精确的几何形状，包括UFF分子力学和AMI半经验方法，这建议了一种便宜且有效的方式来优化圆锥形交叉点的几何形状。此外，ONIOM允许用于评估激发态的局域性，提供对所涉及物理过程的一些基本了解。

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