Program Capabilities

       This code performs simulations of pure liquids and liquids composed by different types of molecules, using the Metropolis Monte Carlo method (MC).

       All molecules have rigid geometry. The total number of molecules N and the temperature T are fixed, but either the volume V or the pressure P can fluctuate during the simulation. One of the NVT or NPT ensembles can be chosen. The intermolecular atomic interaction is described by the sum of the Lennard-Jones and the Coulomb potentials. The border effects are avoided through the use of the image method with periodic boundary conditions. This method allows each molecule to interact with an infinite number of molecule images. However, considering the computational limits and the inclusion of periodicity in the system, each molecule is restricted to interact up to a cutoff radius. In the way that, each molecule sees either the molecule or the respective image, not simultaneously both. In the energy calculation, the error caused by the cutoff radius is reduced with the calculation of the long range correction (LRC) of the potential. The LRC of the Lennard-Jones potential is evaluated using the pair radial distribution function and the LRC of the Coulomb potential is evaluated using the reaction field method in dipole interactions. One MC step is defined after attempt to move N molecules randomly selected. During the simulation, basically four quantities are evaluated and accumulated: the radial distribution function (RDF), the potential energy, U, the first and second virial function, W and Θ, respectively. The atomic coordinates are also storage in a file with XYZ format.

       At the end of simulation relevant thermodynamic properties are calculated using the fluctuation theory and other information of interest are printed out at output files, including configurations of the system that can be easily used for further studies of solvent effects by quantum mechanical calculations.