Comparison of the Standard 6-31G and Binning-Curtiss Basis Sets for Third Row Elements

Abstract

Ab initio calculations were carried out for isogyric reactions involving the third row elements, Ga, Ge, As, Se, and Br. Geometries of all the reactants and products were optimized at the HF, MP2, and B3LYP levels of theory using the 6-31G(d) and 6-31G(d,p) basis sets. For molecules containing third row elements geometries, frequencies and thermodynamic properties were calculated using both the standard 6-31G and the Binning-Curtiss (BC6-31G) basis sets. In order to determine the performance of these basis sets, the calculated thermodynamic properties were compared to G3MP2 values and where possible to experimental values. Geometries and frequencies calculated with the standard 6-31G and the BC6-31G basis sets were found to differ significantly. Frequencies calculated with the standard 6-31G basis set were generally in better agreement with the experimental values (MAD=40.1 cm(-1) at B3LYP/6-31G(d,p) and 94.2 cm(-1) at MP2/6-31G(d,p) for unscaled frequencies and 29.6 cm(-1) and 24.4 cm(-1), respectively, for scaled frequencies). For all the reactions investigated, the thermodynamic properties calculated with the standard 6-31G basis set were found to consistently be in better agreement with the G3MP2 and the available experimental results. However, the BC6-31G basis set performs poorly for the reactions involving both second and third row elements. Since, in general, the standard 6-31G basis set performs well for all the reactions, we recommend that the standard 6-31G basis set be used for calculations involving third row elements. Using G3MP2 enthalpies of reaction and available experimental heats of formation (ΔHf), previously unknown ΔHf for CH3SeH, SiH3SeH, CH3AsH2, SiH3AsH2, CH3GeH3, and SiH3GeH3 were found to be 18.3, 18.0, 38.4, 82.4, 41.9, and 117.4 kJ mol(-1), respectively.

The Fourier transform microwave spectrum of the arsenic dicarbide radical (CCAs: X̃Π1∕22) and its C13 isotopologues

“…The theoretical value of the C-C bond length in CCAs, r C-C = 1.2933 Å, calculated with density functional methods at the B3LYP/aug-cc-pVTZ level, 18 is in reasonable agreement, as well as r C-As = 1.7341 Å, determined from the laser-induced fluorescence ͑LIF͒ experiments of Wei et al 18 Table V also summarizes the C-As and C-C bond lengths of other relevant molecules. 15,17,18,20,[25][26][27][28][29] The ethylene C-C bond length of 1.339 Å is representative for a C v C double bond, while the acetylene C-C bond length, 1.202 Å, is typical of a C w C triple bond. Our experimental C-C bond distance of 1.287 Å for CCAs falls almost midway between the double and triple bond values.…”

Computational Study of Geometry, Solvation Free Energy, Dipole Moment, Polarizability, Hyperpolarizability and Molecular Properties of 2-Methylimidazole

“…All calculations were conducted with the Gaussian 09 software package [19]. From previous work [20,21], it was found that geometries, solvation free energies, dipole moment and molecular properties of similar systems obtained using the B3LYP/6-31G(d,p) showed better agreement with experiments. Therefore, methylimidazole geometries were optimized at the B3LYP electronic structure method [22][23][24] using the 6-31G(d,p) basis set.…”

Structural and Vibrational Studies (FT-IR, FT-Raman) of Voglibose Using DFT Calculation

“…Calculations of the title compound were carried out with the Gaussian 03W program [7] using B3LYP/6-31G(d,p) basis set to predict the molecular structure and vibrational wave numbers and a scaling factor of 0.9608 is used for obtaining a considerably better agreement with experimental data [8,9]. The assignments of the calculated wave numbers are aided by the animation option of the VEDA4 [10] program.…”