Toward accurate prediction of amino acid derivatives structure and energetics from DFT: glycine conformers and their interconversions

Accuracy and Reliability in the Simulation of Vibrational Spectra: A Comprehensive Benchmark of Energies and Intensities Issuing From Generalized Vibrational Perturbation Theory to Second Order (GVPT2)

“…To conclude this analysis of the quality of vibrational spectra computed at the GVPT2 level with DFT-based electronic structure calculation methods, we consider the IR spectrum of glycine, which has been extensively studied by some of us (Biczysko et al, 2012;Barone et al, 2013aBarone et al, , 2013bBarone et al, , 2013c. The molecule has several stable conformers (Shu et al, 2020) and the first two modes, related to torsions around the C-N and C-C bonds, are large amplitude motions (LAMs), which can be poorly described by quartic force fields in rectilinear coordinates. VPT2 is known to perform badly in these conditions, giving very inaccurate energies for these vibrations, as well as for any mode coupled with them.…”

Elucidating active sites and decomposition mechanisms for oxythiomolybdate clusters (Mo2O2Sx, x = 6;8) as catalyzers for hydrogen evolution reactions

“…[32][33][34][35][36][37] The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were first calculated using different methods and basis set for Mo 2 O 2 S 6 in vacuum (Figure S1). MP2 methods can be considered as a highly accurate methods in a large range of application, [38][39][40][41] however, is computationally expense. Therefore in this study, we used MP062X because it reduces the computational costs and has the most similar HOMO and LUMO energy values as MP2 method, when compared with other…”

Structural and Energetic Properties of Amino Acids and Peptides Benchmarked by Accurate Theoretical and Experimental Data

“…29,31,32,46,47 The composite strategy can be rigorously applied into the computation of electronic energies and the energy gradient, while an alternative route, validated on the empirical basis for covalent molecules, exploits direct extrapolation of structural or other molecular parameters. 31,48 The CCSD(T)/CBS+CV scheme combining the extrapolation to the complete basis set (CBS) limit of the Hartree−Fock (HF-SCF) component with the CCSD(T) correlation part computed within frozen-core (fc) approximation, and subsequently including the core−valence (CV) correlation correction is well tested and known to be remarkably accurate for both geometries and corresponding energies, 52,53 but its applicability is limited to small molecules. The possible extrapolation schemes include either a 3-point exponential formula 49 or a 2-point expression, 50,51 notably because the convergence behavior of HF energy is exponentialsquare 54−56 the three-parameter formulas generally do not perform superior to simpler two-parameter ones.…”