Use of deperturbed and generalized second-order vibrational perturbation theories to study vibrational spectra intensity and the role of cubic force constant and total anharmonic matrix contributions to anharmonicity: α-thujone and S-camphor

• Published in: Chemical physics letters Vol. 857; p. 141690
• Main Author: Ziadi, Kamal
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 16-12-2024
• Subjects: Anharmonicity; cubic force constant (CFC); DVPT2; GVPT2; χ-matrix; χ-matrix; DVPT2; Anharmonicity; GVPT2; cubic force constant (CFC)
• ISSN: 0009-2614
• DOI: 10.1016/j.cplett.2024.141690

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•Examines vibrational spectra of α-thujone and S-camphor using DVPT2 and GVPT2 in IR, VCD, and Raman spectra.•Analyzes spectral ranges 3200-2800 cm⁻¹ and 1800-500 cm⁻¹, assessing DVPT2 and GVPT2 performance.•Focuses on anharmonicity using cubic force constants and total 4-anharmonic χ matrix, visualized with heat maps.•Provides insights into dipole and polarizability tensor calculations, highlighting deperturbed transitions.
Herein, we employ deperturbed second-order vibrational perturbation theory (DVPT2) and generalized VPT2 (GVPT2) methodologies to predict and analyze two distinct spectral regions in the infrared, VCD, and Raman spectra of α-thujone and S-camphor. The first spectral region spans from 3200 to 2900 cm−1, while the second region extends from 1800 to 500 cm−1. We aim to introduce and validate a program for the simultaneous analysis of vibrational spectra intensity in medium-sized molecules using GVPT2 and DVPT2. Furthermore, employing a graphical presentation (heat map) to illustrate the important contribution of cubic force constant and χ-matrix to anharmonicity.