Modeling and spectral simulation of formic acid dimer in Ar matrix using ONIOM calculations

Abstract

The supermolecule approach has been used to model molecules embedded in a solid argon matrix. The interaction between the guest and the host atoms in the first solvation shell (FSS) are evaluated using density functional calculations while that beyond the FSS is incorporated using ONIOM calculations to extend the results of our previous study [F. Ito, J. Chem. Phys. 133 (2010) 214502]. The vibrational spectra of a formic acid dimer (FAD) in an Ar matrix was simulated using (FAD)-Arn clusters (n = 94–1095). Structural relaxation in the first solvation shell is crucial to quantitatively reproduce the matrix shifts of fundamental bands, according to calculations at the B971/6-31++G(3df,3pd) level. Moreover, the influence of the outer Ar atoms is negligible.