Calculation of the Structure of (CH₃CN)_n and (CH₃CN)_m·H₂O Clusters by Density Functional Theory

The geometry and energy of (CH₃CN)_n (n = 2-8) and (CH₃CN)_m·H₂O (m = 4-7) clusters are calculated by the density functional theory with the B3LYP functional, the cc-pvdz basis set and Grimme’s dispersion correction D3. In (CH₃CN)_n clusters at n ≤ 4, acetonitrile molecules are arranged antiparallel; as n increases, cycles can be distinguished in the cluster structure with the head-to-tail orientation of molecules. Cycles can be distinguished where the molecules have a head-to-tail orientation. With the same number of molecules in a cluster the formation of clusters including a water molecule is more energetically favorable. Starting from m > 5, this molecule is located inside the cavity of acetonitrile molecules. The application of Grimme D3 correction allows us to refine the energy of the formation of (CH₃CN)₃ clusters.