Curtiss Larry A, Redfern Paul C, Raghavachari Krishnan
Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
J Chem Phys. 2007 Feb 28;126(8):084108. doi: 10.1063/1.2436888.
The Gaussian-4 theory (G4 theory) for the calculation of energies of compounds containing first- (Li-F), second- (Na-Cl), and third-row main group (K, Ca, and Ga-Kr) atoms is presented. This theoretical procedure is the fourth in the Gaussian-n series of quantum chemical methods based on a sequence of single point energy calculations. The G4 theory modifies the Gaussian-3 (G3) theory in five ways. First, an extrapolation procedure is used to obtain the Hartree-Fock limit for inclusion in the total energy calculation. Second, the d-polarization sets are increased to 3d on the first-row atoms and to 4d on the second-row atoms, with reoptimization of the exponents for the latter. Third, the QCISD(T) method is replaced by the CCSD(T) method for the highest level of correlation treatment. Fourth, optimized geometries and zero-point energies are obtained with the B3LYP density functional. Fifth, two new higher level corrections are added to account for deficiencies in the energy calculations. The new method is assessed on the 454 experimental energies in the G305 test set [L. A. Curtiss, P. C. Redfern, and K. Raghavachari, J. Chem. Phys. 123, 124107 (2005)], and the average absolute deviation from experiment shows significant improvement from 1.13 kcal/mol (G3 theory) to 0.83 kcal/mol (G4 theory). The largest improvement is found for 79 nonhydrogen systems (2.10 kcal/mol for G3 versus 1.13 kcal/mol for G4). The contributions of the new features to this improvement are analyzed and the performance on different types of energies is discussed.
本文提出了用于计算含第一周期（Li - F）、第二周期（Na - Cl）和第三周期主族（K、Ca和Ga - Kr）原子的化合物能量的高斯 - 4理论（G4理论）。该理论方法是基于一系列单点能量计算的高斯 - n量子化学方法系列中的第四个。G4理论在五个方面对高斯 - 3（G3）理论进行了修正。第一，使用外推程序来获得用于总能量计算的哈特里 - 福克极限。第二，将d极化集在第一周期原子上增加到3d，在第二周期原子上增加到4d，并对后者的指数进行重新优化。第三，将最高级别的相关处理方法从QCISD(T)方法替换为CCSD(T)方法。第四，使用B3LYP密度泛函获得优化的几何结构和零点能。第五，添加了两个新的高级校正以弥补能量计算中的不足。在G305测试集[L. A. Curtiss, P. C. Redfern, and K. Raghavachari, J. Chem. Phys. 123, 124107 (2005)]中的454个实验能量上对新方法进行了评估，与实验的平均绝对偏差从1.13 kcal/mol（G3理论）显著提高到0.83 kcal/mol（G4理论）。对于79个非氢体系发现了最大的改进（G3为2.10 kcal/mol，G4为1.13 kcal/mol）。分析了新特征对这种改进的贡献，并讨论了在不同类型能量上的性能。
