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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >How Well Can Hybrid Density Functional Methods Predict Transition State Geometries and Barrier Heights?
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How Well Can Hybrid Density Functional Methods Predict Transition State Geometries and Barrier Heights?

机译：混合密度泛函方法如何很好地预测过渡态的几何形状和势垒高度？

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We compare hybrid Hartree-Fock density-functional theory to ab initio approaches for locating saddle point: geometries and calculating barrier heights on a Born-Oppenhiemer potential energy surface. We located reactant, product, and saddle point stationary points for 22 reactions by the MP2 and QCISD ab initio methods and the B3LYP, BH&HLYP, mPWIPW91, and MPWIK hybrid Hartree-Fock DFr methods. We examined all of these methods with two basis sets, 6-31+G(d,p) and MG3. By comparison to calculations on five systems where the saddle point has been optimized at a high level of theory , we determined that the best , saddle point geometries were obtained using the MPW1K and QCISD levels of theory. Of the methods tested; mPWIPW91 and B3L YP are the least effective for determining saddle point geometries and have mean unsigned error in barrier heights of 3.4-4..2 kcaVmol, depending on the basis set. In contrast, the MPWIK.:.: level of theory predicts the most accurate saddle point geometries and has a mean unsigned error of only 1.5 kcal/mol for either basis set. For even better accuracy, the combination of MPWIK/6-31 +G(d,p) geometry calculations with QCISD(T)/MG3 or CCSD(T)/MG3 single-point energy calculations is shown to have an excellent performance-to-cost ratio. As a side product of this work, we report optimized scale factors for computing zero point energies by MPWIK.
机译：我们将混合Hartree-Fock密度泛函理论与从头算位置的鞍点方法进行了比较：确定几何形状并计算Born-Oppenhiemer势能面上的势垒高度。我们通过MP2和QCISD从头算方法以及B3LYP，BH＆HLYP，mPWIPW91和MPWIK混合Hartree-Fock DFr方法确定了22个反应的反应物，产物和鞍点固定点。我们使用6-31 + G（d，p）和MG3这两个基集检查了所有这些方法。通过与在较高理论水平上优化了鞍点的五个系统的计算进行比较，我们确定使用MPW1K和QCISD理论水平可以获得最佳的鞍点几何形状。经测试的方法; mPWIPW91和B3L YP对于确定鞍点几何形状最不有效，并且根据基准集，势垒高度的平均无符号误差为3.4-4..2 kcaVmol。相比之下，MPWIK。：。：理论水平可以预测最准确的鞍点几何形状，并且对于任一基准集，其平均无符号误差仅为1.5 kcal / mol。为了获得更高的精度，MPWIK / 6-31 + G（d，p）几何计算与QCISD（T）/ MG3或CCSD（T）/ MG3单点能量计算的结合被证明具有出色的性能-成本比。作为这项工作的副产品，我们报告了MPWIK用于计算零点能量的优化比例因子。

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