Work

Anharmonicity in Molecular Crystals: Generalized Perturbation Theory Meets Periodic Computations

Year: 2025

Type: article

Abstract: Accurate simulation of vibrational spectra in the solid state remains a major challenge due to the combined effects of anharmonicity, intermolecular interactions, and resonance phenomena. In this work, we introduce a generalized second-order vibrational perturbation theory (GVPT2) framework for the quantitative computational spectroscopy of molecular solids. The method balances efficiency and accuracy through a perturb-then-diagonalize approach in which resonant terms are excluded in the initial perturbative treatment and subsequently handled more accurately through a variational approach. This strategy ensures numerical stability while capturing essential vibrational couplings. As a representative application, we investigated the infrared spectrum of solid carbon dioxide (dry ice), a prototypical system exhibiting strong anharmonic effects and Fermi resonances. The generalized VPT2 approach accurately reproduces both absolute band positions and splitting patterns, yielding results in excellent agreement with the experimental data. These findings demonstrate the potential of the method for reliable and transferable anharmonic vibrational analysis across a broad class of solid-state systems.

Source: The Journal of Physical Chemistry Letters

DOI: 10.1021/acs.jpclett.5c02217

Authors: Davide Mitoli, Alessandro Erba, Vincenzo Barone, Marco Mendolicchio

Institutions: University of Turin, National Interuniversity Consortium of Materials Science and Technology, Scuola Normale Superiore

Language: English

Topic: Spectroscopy and Quantum Chemical Studies

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funders: Dipartimenti di Eccellenza, Ministero dell’Istruzione, dell’Università e della Ricerca