A Validation of Cluster Modeling in the Description of Matrix Isolation Spectroscopy

Abstract

Matrix isolation is a fundamental tool for the synthesis and characterization of highly reactive novel species and investigation of unusual bonding situations. Ab initio descriptions of guest-host interactions in matrix isolation are highly demanding, as the weak interactions between guest and host can influence the former's oftentimes challenging electronic structure. In this study, the matrix effects on a single CO 2 molecule in an argon matrix were investigated with dispersion-corrected density functional theory calculations. Three different guest-host structures were described by bulk models employing periodic boundary conditions as well as cluster models. The calculations were analyzed with respect to structural features of the CO 2 molecule and its immediate surroundings. Also, the molecule's harmonic frequencies were determined. The calculated frequencies were in qualitative agreement with experimental observations. The cluster models produced comparable results given that the clusters were large enough to reproduce the structural features of the bulk model.

Decomposing anharmonicity and mode-coupling from matrix effects in the IR spectra of matrix-isolated carbon dioxide and methane

“…This approach has recently been applied in a theoretical study of CO 2 in argon within the harmonic approximation, showing promising results. 44 The agreement with experimental spectra would further profit from incorporation of anharmonicity and mode-coupling in the calculations. At this level, most matrix effects should be predictable from theory with high accuracy.…”

“…On the other side, approaches for an efficient and accurate calculation of various host-guest combinations rely on approximations that limit the incorporation of different matrix effects and anharmonicity. Some approaches based on molecular dynamics, 42 vibrational self-consistent field 43 and density functional theory 44 have been investigated.…”

Increase of Radiative Forcing through Midinfrared Absorption by Stable CO2 Dimers?

“…Matrix effects could be computationally modeled by including the matrix atoms explicitly. 40 In the present work, however, we rely on comparing shifts of bands rather than absolute wavenumbers. This strategy largely eliminates the impact of matrix effects on our comparison of experimental and computational IR spectra.…”

Theoretical modeling of molecules in weakly interacting environments: trifluoride anions in argon

“…Concerning the extent of the guest-host system an obvious, tested approach would be the use of density functional theory (DFT) methods. [21][22][23] However, this is not applicable due to the delicate electronic structure of the trifluoride. Alternatives to a DFT description of the complete system are wave function embedding methods or a many-body expansion (MBE) of the potential energy surface.…”