A quantum molecular dynamics study of aqueous solvation dynamics

P. E. VIDELA, P. J. ROSSKY, D. LARIA

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2013 vol. 139 p. 164506 - 164506

0021-9606

Ring polymer molecular dynamics experiments have been carried out to examineeffects derived from  nuclear quantum fluctuations at ambient conditions on equilibrium andnon-equilibrium dynamicalcharacteristics of charge solvation by a popular simple, rigid, water  SPC/E model, and for a morerecent, and flexible  q-TIP4P/F  model, to examine the generality of conclusions.In particular, we have recorded the relaxation of the solvent energy gapfollowing instantaneous, $pm e$ charge jumps in an initially unchargedLennard-Jones-like solute. In both charge cases, quantum effects are reflectedin sharper decays at the initial stages of the relaxation, which produce up toa $sim 20%$ reduction in the characteristic timescales describingthe solvation processes.  For anionic solvation, the magnitude ofpolarization fluctuations controlling the extent of the water protonlocalization in the first solvation shell is somewhat more marked than for cations,bringing the quantum solvation process closer to the classical case.Effects on the solvation response from the explicit incorporation of flexibilityin the water Hamiltonian are also examined.Predictions from linear response theories for the overall relaxation profileand for the corresponding characteristic timescales are reasonably accuratefor the solvation of cations, whereas we find that they are much less satisfactory for the anionic case.