Born-Oppenheimer molecular dynamics and electronic properties of liquid H2S: The importance of a non-local approach to dispersion interactions

Abstract

The dynamics and electronic properties of liquid H2S were investigated by Born–Oppenheimer molecular dynamics (BOMD). The Vydrov and Van Voorhis VV10 exchange–correlation functional [J. Chem. Phys. 133 (2010) 244103] that includes non-local correlation was adopted for generating the dynamics. This functional predicts the binding energy of the (H2S)2 dimer in very good agreement with experiment. Emphasis was placed on the structure, polarisation effects, and electronic absorption in liquid phase. The dipole moment in liquid H2S increases by 0.2D relative to the gas phase. A very small change (∼0.1 eV) in the position of the first maximum of the electronic absorption spectrum is observed when we compare liquid H2S and the isolated molecule. This is in contrast to liquid water where a [0.4-0.7] eV blue shift in the first peak of the absorption spectrum relative to the gas phase is observed. Exciton binding energies of H2S are calculated and compared with results for water. Their importance for explaining the difference between the blue-shift in H2S and water is discussed. The results indicate that although the (H2S)2 dimer is HB, some specific features characterising the structure and electronic properties of other HB liquids are not observed in liquid H2S. The interest of a non-local treatment of van der Waals interactions in liquid H2S is stressed.