Molecular modelling encompasses all ways, theoretical and procedure, wont to model or mimic the behaviour of molecules. The ways square measure utilized in the fields of procedure chemistry, drug style, procedure biology and materials science to review molecular systems starting from little chemical systems to giant biological molecules and material assemblies. the best calculations may be performed by hand, however inevitably computers square measure needed to perform molecular modelling of any moderately sized system. The common feature of molecular modelling ways is that the atomistic level description of the molecular systems. this could embrace treating atoms because the smallest individual unit (a molecular mechanics approach), or expressly modelling protons and neutrons with its quarks, anti-quarks and gluons and electrons with its photons (a quantum chemistry approach). Molecular mechanics is one side of molecular modelling, because it involves the utilization of mechanics (Newtonian mechanics) to explain the physical basis behind the models. Molecular models generally describe atoms (nucleus associate degreed electrons collectively) as purpose charges with an associated mass. The interactions between neighboring atoms square measure delineate by spring-like interactions (representing chemical bonds) and Van der Waals forces.