Molecular-dynamic calculation of spectral characteristics of absorption of infrared radiation by $(\mathrm{H}_2\mathrm{O})_j$ and $(\mathrm{CH}_4)_i(\mathrm{H}_2\mathrm{O})_n$ clusters

The method of molecular dynamics is used to investigate the stability and physical properties of $(\mathrm{CH}_4)_i(\mathrm{H}_2\mathrm{O})_n$ clusters. The possibility of methane molecules being absorbed by clusters containing ten and twenty water molecules is demonstrated. Such clusters retain the thermodynamic stability when the number of $\mathrm{CH}_4$ molecules they absorbed does not exceed six. The frequency dispersion of complex permittivity of $(\mathrm{CH}_4)_i(\mathrm{H}_2\mathrm{O})_n$ aggregates reflects the resonant behavior of polarizability depending on the applied electric field. The dependence of the absorption coefficient $\alpha$ on the frequency of infrared radiation varies significantly after even one $\mathrm{CH}_4$ molecule is absorbed by water clusters. The maximal value of $\alpha$ for water aggregates which absorbed $\mathrm{CH}_4$ molecules is much lower than the respective value for pure water clusters of appropriate size.