Modelling trapping sites of (HF)2 in argon clusters

Molecular dynamics simulations have been performed for (HF)2 · Ar62 heteroclusters to compare the structural and dynamical properties of (HF)2 in different argon environments. Several minimum energy arrangements which mimic different trapping sites of (HF)2 in argon related to the matrix isolation and cluster adsorption experimental conditions have been analysed. The potential energy surface of the system has been constructed as a superposition of diatomics-in-molecules potentials for all ArHF triangles, the Quack-Suhm SQSBDE potential for (HF)2 and pairwise ArAr interaction potentials. Of special interest is a comparison of the configuration in the centre of argon shells and those on the surface of argon clusters. Argon-induced vibrational shifts in (HF)2 with respect to the naked hydrogen fluoride dimer have been computed for each trapping site. The experimental difference in the HF stretch frequency shifts for (HF)2 in the matrix and on the surface of argon clusters is precisely reproduced.