Assessment of G3(MP2)//B3 theory including a pseudopotential for molecules containing first-, second-, and third-row representative elements

Abstract

G3(MP2)∕∕B3 theory was modified to incorporate compact effective potential (CEP) pseudopotentials, providing a theoretical alternative referred to as G3(MP2)∕∕B3-CEP for calculations involving first-, second-, and third-row representative elements. The G3∕05 test set was used as a standard to evaluate the accuracy of the calculated properties. G3(MP2)∕∕B3-CEP theory was applied to the study of 247 standard enthalpies of formation, 104 ionization energies, 63 electron affinities, 10 proton affinities, and 22 atomization energies, comprising 446 experimental energies. The mean absolute deviations compared with the experimental data for all thermochemical results presented an accuracy of 1.4 kcal mol(-1) for G3(MP2)∕∕B3 and 1.6 kcal mol(-1) for G3(MP2)∕∕B3-CEP. Approximately 75% and 70% of the calculated properties are found with accuracy between ±2 kcal mol(-1) for G3(MP2)∕∕B3 and G3(MP2)∕∕B3-CEP, respectively. Considering a confidence interval of 95%, the results may oscillate between ±4.2 kcal mol(-1) and ±4.6 kcal mol(-1), respectively. The overall statistical behavior indicates that the calculations using pseudopotential present similar behavior with the all-electron theory. Of equal importance to the accuracy is the CPU time, which was reduced by between 10% and 40%.

G3(MP2)-CEP theory and applications for compounds containing atoms from representative first, second and third row elements of the periodic table

“…Atomization energies were also considered for compounds containing third row elements. Table 1 shows the optimal HLC parameters for the G3(MP2)-CEP, G3(MP2)//B3-CEP [16] and G3CEP [14,15] theories. The first general trend was that the HLC parameters were larger for G3(MP2)-CEP, G3(MP2), G3(MP2)//B3-CEP and G3(MP2)//B3-CEP than for G3 and G3CEP.…”

“…G3(MP2) is based primarily on geometries optimized at the Hartree-Fock/6-31G(d) level of theory, and further improved by optimization at the MP2(full)/6-31G(d) level using all electrons for the calculation of correlation effects, while G3(MP2)//B3 uses geometries optimized at the B3LYP/6-31G(d) level. The adaptation of pseudopotentials to the G3(MP2) theory was carried out in a similar manner to that introduced in the G3(MP2)//B3-CEP theory [16] and consisted of the adaptation of the basis sets and the reoptimization of the HLC parameters following the procedure used previously for the G3CEP and G3(MP2)//B3 theories [15,16]. Since the methodologies were similar, the 6-31G(d) and G3MP2large basis set adapted for use with G3(MP2)-CEP were the same as those used with G3(MP2)// B3-CEP [16].…”

“…The adaptation of pseudopotentials to the G3(MP2) theory was carried out in a similar manner to that introduced in the G3(MP2)//B3-CEP theory [16] and consisted of the adaptation of the basis sets and the reoptimization of the HLC parameters following the procedure used previously for the G3CEP and G3(MP2)//B3 theories [15,16]. Since the methodologies were similar, the 6-31G(d) and G3MP2large basis set adapted for use with G3(MP2)-CEP were the same as those used with G3(MP2)// B3-CEP [16]. The adaptation from the all-electron basis set to the pseudopotential is discussed in detail in the literature [14,15] and will not be reproduced here.…”

“…Examples of this second perspective are found in modifications of the G3 theory, for example, G3(MP2) [5,6] and G3(MP2)//B3 [13]. These reduced-order methods have been guided by the following principles: (1) third-and fourth-order perturbation calculations with large basis sets are avoided; (2) In addition to the reduced-order alternatives, computational costs can be minimized by using pseudopotentials, such as in the G3CEP [14,15] and G3(MP2)//B3-CEP [16] theories. These new composite theories present a significant reduction in computational demand while maintaining an accuracy similar to that of the respective all-electron versions, and have been applied not only to calculating thermochemical properties but also to other molecular properties [17,18].…”

“…The choice for CEP was based on the simplicity of the pseudopotential, its availability for the largest number of elements of the periodic table, applications in the literature and successful adaptation in previous works [14][15][16].…”