When is a molecule properly solvated by a continuum model or in a cluster ansatz? A first-principles simulations of alanine hydration

The first-principles molecular dynamics simulations of the alanine hydration was carried out to test the validity of the cluster ansatz approach and the continuum model approach. Sufficient convergence of the cluster ansatz approach is observed for either of the two solvent shells around the polar groups and one solvent shell around the apolar groups or two solvent shells around the polar groups surrounded by a dielectric continuum.