Influence of diffuse and polarization functions on the second-order Moller-Plesset optimized dihedral angle of biphenyl
Influence of diffuse and polarization functions on the second-order Moller-Plesset optimized dihedral angle of biphenyl
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DOI：
10.1007/s00214-003-0429-3
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发表时间：
2003-06-01
影响因子：
1.7
通讯作者：
Grein, F
中科院分区：
文献类型：
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作者：
Grein, F
使用6-31G和6-311G基组(共16个基组)，对联苯进行了Hartree-Fock(HF)、MP2和B3LYP几何优化。对于MP2方法，漫反射函数使二面角Phi从46.3度(6-31G)增加到54.1度(6-311++G)，而极化函数降低了二面角，例如6-311++G(2d，2p)从54.1度增加到42.1度。对于单组极化函数，Phi(MP2)接近或高于Phi(HF)(44-47度)，但对于双组，它低于Phi(HF)，并接近B3LYP值(38-42度)，这表明它与基组几乎没有相关性。最可靠的phi值为42.1度[MP2/6-311++G(2d，2p)]，预计随着添加更多的漫反射函数，该值将略有增加。相应的0度(共面构象)的最佳计算能垒为2.83千卡/摩尔，远高于实验值(1.4+/-0.5千卡/摩尔)。90度时的势垒为1.82千卡/摩尔，与实验值(1.6+/-0.5千卡/摩尔)和以前的理论结果一致。
Using 6-31G and 6-311G basis sets to which diffuse and polarization functions were added in a stepwise fashion (a total of 16 basis sets), Hartree-Fock (HF), MP2 and B3LYP geometry optimizations were performed on biphenyl. With the MP2 method, diffuse functions raise the dihedral angle phi, for example, from 46.3degrees for 6-31G to 54.1degrees for 6-311++G, while polarization functions lower it, for example, from 54.1degrees for 6-311++G to 42.1degrees for 6-311++G(2d,2p). For a single set of polarization functions, phi(MP2) lies close to or above phi(HF) (44-47degrees), but for a double set it is below phi(HF) and is close to B3LYP values (38-42degrees) which show little basis set dependence. The most reliable value for phi, 42.1degrees [MP2/6-311++G(2d,2p)], is expected to increase slightly by adding more diffuse functions. The corresponding best calculated energy barrier at 0degrees (coplanar conformation) is 2.83 kcal/mol, much higher than the experimental estimate (1.4 +/- 0.5 kcal/mol). The barrier at 90degrees is 1.82 kcal/mol, in line with the experimental estimate (1.6 +/- 0.5 kcal/mol) and with previous theoretical results.