An instantaneous normal mode theory of condensed phase absorption: the vibrational spectrum of condensed CS2 from boiling to freezing

An instantaneous normal mode (INM) theory of condensed phase absorption is applied to determine the infrared spectrum of condensed phase carbon disulfide (CS2). State points with pressures from 100 kPa (near boiling) to 1.16 GPa (near freezing) are considered, and excellent agreement with time correlation function (TCF) and experimental results is demonstrated. The INM theory includes an approximate treatment of the imaginary INM absorption, and reproduces the Fourier transform of the full system dipole–dipole TCF. The INM formalism also allows for more flexibility in calculating the spectrum, and is far less computationally demanding.