We describe a new approach based on semiclassical molecular dynamics that allows simulating infrared absorption or emission spectra of molecular systems with inclusion of anharmonic intensities. This is achieved from semiclassical power spectra by computing first the vibrational eigenfunctions as a linear combination of harmonic states, and then the oscillator strengths associated with the vibrational transitions. We test the approach against a 1D Morse potential and apply it to the water molecule with results in excellent agreement with discrete variable representation quantum benchmarks. The method does not require any grid calculations, and it is directly extendable to high dimensional systems. The usual exponential scaling of the basis set size with the dimensionality of the system can be avoided by means of an appropriate truncation scheme. Furthermore, the approach has the advantage to provide IR spectra beyond the harmonic approximation without losing the possibility of an intuitive assignment of absorption peaks in terms of normal modes of vibration.

Anharmonic vibrational eigenfunctions and infrared spectra from semiclassical molecular dynamics / M. Micciarelli, R. Conte, J. Suarez, M. Ceotto. - In: THE JOURNAL OF CHEMICAL PHYSICS. - ISSN 0021-9606. - 149:6(2018 Aug 14).

Anharmonic vibrational eigenfunctions and infrared spectra from semiclassical molecular dynamics

Micciarelli, Marco;Conte, Riccardo;Suarez, Jaime;Ceotto, Michele
2018-08-14

Abstract

We describe a new approach based on semiclassical molecular dynamics that allows simulating infrared absorption or emission spectra of molecular systems with inclusion of anharmonic intensities. This is achieved from semiclassical power spectra by computing first the vibrational eigenfunctions as a linear combination of harmonic states, and then the oscillator strengths associated with the vibrational transitions. We test the approach against a 1D Morse potential and apply it to the water molecule with results in excellent agreement with discrete variable representation quantum benchmarks. The method does not require any grid calculations, and it is directly extendable to high dimensional systems. The usual exponential scaling of the basis set size with the dimensionality of the system can be avoided by means of an appropriate truncation scheme. Furthermore, the approach has the advantage to provide IR spectra beyond the harmonic approximation without losing the possibility of an intuitive assignment of absorption peaks in terms of normal modes of vibration.
Semiclassical, spectroscopy, eigenfunctions, absorption, emission, IR
Settore CHIM/02 - Chimica Fisica
Divide and Conquer ad initio semiclassical molecular dynamics for spectropic calculations of complex systems (SEMICOMPLEX)
THE JOURNAL OF CHEMICAL PHYSICS
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/599437
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