Finite temperature path integral Monte Carlo simulations of structural and dynamical properties of ArN−CO2 clusters

Abstract

We report finite temperature quantum mechanical simulations of structural and dynamical properties of Ar(N)-CO(2) clusters using a path integral Monte Carlo algorithm. The simulations are based on a newly developed analytical Ar-CO(2) interaction potential obtained by fitting ab initio results to an anisotropic two-dimensional Morse/Long-range function. The calculated distributions of argon atoms around the CO(2) molecule in Ar(N)-CO(2) clusters with different sizes are consistent to the previous studies of the configurations of the clusters. A first-order perturbation theory is used to quantitatively predict the CO(2) vibrational frequency shift in different clusters. The first-solvation shell is completed at N = 17. Interestingly, our simulations for larger Ar(N)-CO(2) clusters showed several different structures of the argon shell around the doped CO(2) molecule. The observed two distinct peaks (2338.8 and 2344.5 cm(-1)) in the υ(3) band of CO(2) may be due to the different arrangements of argon atoms around the dopant molecule.

Observing the Completion of the First Solvation Shell of Carbon Dioxide in Argon from Rotationally Resolved Spectra

“…CO 2 -Ar 15 has five argon rings around the CO 2 axis, each consisting of three Ar atoms. This agrees with Wang and Xie , and probably with Severson and Böyükata et al as well, though it is difficult to be sure from their figures. CO 2 -Ar 17 has three concentric rings, each consisting of five Ar atoms plus two additional Ar atoms, one located at each end.…”

“…1 Detailed understanding of such phenomena at the microscopic level is essential for manipulation of chemical reactions, modulating biological activities and solvation effects. In the particular case of the CO2-Arn system, there have been at least six publications concerned with theoretical structures, [2][3][4][5][6][7] but there are no experimental results for clusters beyond n = 2. Direct high-level ab initio calculations become very challenging for larger clusters (many electrons!).…”

“…36 We carried out our own cluster calculations 34 since those in the literature [2][3][4][5][6] often do not include full details on bond lengths, rotational constants, and binding energies. For these, we used the Ar-Ar interaction potential of Dieters and Sadus, 37 together with the ab initio CO2-Ar potential energy surfaces for the CO2 ground and v3 = 1 states as calculated by Cui et al 23 Since the same CO2-Ar potential was used by Wang and Xie for their CO2-Arn calculations, 6,7 our cluster results are similar to theirs (with small differences in calculated binding energies due to the use of different Ar-Ar potentials).…”

“… a PIMC (path integral Monte Carlo) and QMC (quantum Monte Carlo) shifts were estimated from Figure 6 of ref . …”