A new implementation of the conductor-like screening
solvation model (COSMO) in the GAUSSIAN94
package is presented. It allows Hartree−Fock (HF), density
functional (DF) and post-HF energy, and HF
and DF gradient calculations: the cavities are modeled on the
molecular shape, using recently optimized
parameters, and both electrostatic and nonelectrostatic contributions
to energies and gradients are considered.
The calculated solvation energies for 19 neutral molecules in
water are found in very good agreement with
experimental data; the solvent-induced geometry relaxation is studied
for some closed and open shell molecules,
at HF and DF levels. The computational times are very
satisfying: the self-consistent energy evaluation
needs a time 15−30% longer than the corresponding procedure in
vacuo, whereas the calculation of energy
gradients is only 25% longer than in vacuo for medium size
molecules.
The conductor-like solvation model, as developed in the framework of the polarizable continuum model (PCM), has been reformulated and newly implemented in order to compute energies, geometric structures, harmonic frequencies, and electronic properties in solution for any chemical system that can be studied in vacuo. Particular attention is devoted to large systems requiring suitable iterative algorithms to compute the solvation charges: the fast multipole method (FMM) has been extensively used to ensure a linear scaling of the computational times with the size of the solute. A number of test applications are presented to evaluate the performances of the method.
The polarizable continuum model (PCM), used for the calculation of molecular energies, structures, and properties in liquid solution has been deeply revised, in order to extend its range of applications and to improve its accuracy. The main changes effect the definition of solute cavities, of solvation charges and of the PCM operator added to the molecular Hamiltonian, as well as the calculation of energy gradients, to be used in geometry optimizations. The procedure can be equally applied to quantum mechanical and to classical calculations; as shown also with a number of numerical tests, this PCM formulation is very efficient and reliable. It can also be applied to very large solutes, since all the bottlenecks have been eliminated to obtain a procedure whose time and memory requirements scale linearly with solute size. The present procedure can be used to compute solvent effects at a number of different levels of theory on almost all the chemical systems which can be studied in vacuo.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.