【摘要】 对《CRC物理与化学手册》第77版中收集的第三周期以前的所有已知实验构型的无机分子的构型 ,在MP2、B3LYP、B3PW91级别上进行了构型优化的系统性比较.优化采用基组为6 31G(d,p) ,6 311G(d,p),6 311G(2d,p).对大多数分子另比较了QCISD(T)方法 ,对多原子分子比较了BPW91方法 ,对含氢双原子分子也使用了QCISD方法.结果表明 ,键长的平均绝对偏差(单位 :pm)由小到大的顺序为 :B3PW91/6 311G(2d,p)(1.50),B3LYP/6 311G(2d,p)(1.73),MP2(full)/6 311G(2d,p)(1.75),B3PW91/6 311G(d,p)(1.82),QCISD(T,FC)/6 311G(d,p)(1.82),B3PW91/6 31G(d)(1.84),MP2(full)/6 311G(d,p)(1.87),MP2(full)/6 31G(d,p)(2.09),B3LYP/6 311G(d,p)(2.11),B3LYP/6 31G(d)(2.12),QCISD(T,FC)/6 31G(d,p)(2.14),BPW91/6 311G(2d,p)(2.88),BPW91/6 31G(d)(3.33)和BPW91/6 311G(d,p)(3.42).键长数目分别为248,248,246,248,187,248,246,246,248,248,187,151,151和151个.更多还原

【Abstract】 A systematic comparative study of theoretical geometry optimization on all of the first and second row gas phase inorganic molecules collected in the 77th ed. CRC Handbook of Chemistry and Physics was carried out. The routinely examined theoretical levels for all of the molecules were the analytical gradient MP2(full),B3LYP and B3PW91 with 6 31G(d),6 31G(d,p),6 311G(d,p) and 6 311G(2d,p) basis sets. Additional examined theoretical levels for the diatomic,tri atomic and most of the poly atomic species were QCISD(T)/6 31G(d,p) and QCISD(T)/6 311G(d,p) numerical optimizations. For the diatomic hydrides,extra numerical QCISD(T)/6 31G(d) and analytical QCISD(full)/6 311G(d,p) optimizations were included. For the poly atomic species,the computationally less expensive BPW91 with three basis sets were alsoexamined. The overall performances of the theoretical methods and the basis sets were analyzed in means of the average deviations (AD) and the average absolutedeviations (AAD). It was shown that all of the theoretical methods re produced the bond angles reasonably well. For the bond lengths at the same basis sets,B3PW91 performed the best,MP2 the next and then B3LYP. 6 311G(d,p) basis sets greatly improved the QCISD(T) results from those of 6 31G(d,p). In all of the theoretical methods examined,BPW91 resulted in the largest AAD errors. The AAD values (in pm) for all of the bond lengths in this study were summarized in Table 7 of the text,e.g.,1.50 for B3PW91/6 311G(2d,p),1.73 for B3LYP/6 311G(2d,p),1.75 for MP2(full)/6 311G(2d,p),1.82 for B3PW91/6 311G(d,p),1.82 for QCISD(T,FC)/6 311G(d,p),1.84 for B3PW91/6 31G(d),1.87 for MP2(full)/6 311G(d,p),2.09 for MP2(full)/6 31G(d,p),2.11 for B3LYP/6 311G(d,p),2.12 for B3LYP/6 31G(d),2.14 for QCISD(T,FC)/6 31G(d,p),2.88 for BPW91/6 311G(2d,p),3.33 for BPW91/6 31G(d) and 3.42 for BPW91/6 311G(d,p),with the number of bond length samples of 248,248,246,248,187,248,246,246,248,248,187,151,151 and 151,respectively.更多还原