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Manuscript Title: ASEP/MD: a program for the calculation of solvent effects combining QM/MM methods and the mean field approximation.
Authors: I.F. Galvan, M.L. Sanchez, M.E. Martin, F.J. Olivares Del Valle, M.A. Aguilar
Program title: ASEP/MD
Catalogue identifier: ADSF_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 155(2003)244
Programming language: Fortran 90.
Computer: Intel based PC, SUN.
Operating system: Red Hat Linux 7.2, SUNOS 5.6.
Keywords: Solvent effects, QM/MM methods, Mean field approximation, Geometry optimization, Molecular, Condensed phase, Simulation.
Classification: 16.13.

Nature of problem:
The study of molecules in solution with quantum methods is a difficult task because of the large number of molecules and configurations that must be taken into account. The quantum mechanies/molecular mechanics methods proposed to date either require massive computational power or oversimplify the solute quantum description.

Solution method:
A non-traditional QM/MM method based on the mean field approximation was developed where a classical molecular dynamics simulation is coupled with a quantum calculation. The average electostatic potential generated by the solvent over the solute is calculated from the simulation and introduced into the quantum calculation as an external field. This process can be performed iteratively. Standard external programs are used for the molecular dynamics simulations and for the quantum calculations. The present program acts as an interface and controls the flow of the calculation.

At present only pure liquids and binary dilute solutions (a single solute molecule) can be studied. For the molecular dynamics only MOLDY is implemented, while GAUSSIAN and HONDO are available for the quantum calculations. Restrictions of the aforementioned programs apply.

Unusual features:
Uses SYSTEM and GETARG calls.

Running time:
Running time depends on the nature of the chemical system and the options passed to the external programs, which are usually by far the longest part of the calculations.