Infrared spectra of inorganic aerosols: ab initio study of (NH_4)_2SO_4, NH_4NO_3, and NaNO_3

摘要

The structures and vibrational spectra of inorganic aerosols, including ammonium sulfate (NH_4)_2SO_4, ammonium nitrate NH_4NO_3, and sodium nitrate NaNO_3 are investigated at the periodic ab initio quantum mechanical level with the CRYSTAL code, which is based on Gaussian basis sets. Local density (LDA), gradient-corrected (PW91), and hybrid (B3LYP) density functionals have been used and the results are compared with experiment. All three functionals reproduce the equilibrium geometry of these aerosols to a high level of accuracy. The calculations of the frequencies gave a mean absolute deviation from experiment of 3% for B3LYP, clearly showing that this functional performs extremely well in this case. The mean absolute deviation is about 7% and 6% for PW91 and LDA, respectively.