Editing Computational chemistry (section)

=== Molecular mechanics ===
{{Main article|Molecular mechanics}}

In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. [[Molecular mechanics]] simulations, for example, use one classical expression for the energy of a compound, for instance, the [[harmonic oscillator]]. All constants appearing in the equations must be obtained beforehand from experimental data or ''ab initio'' calculations.<ref name="Ramachandran-2008" />

The database of compounds used for parameterization, i.e. the resulting set of parameters and functions is called the [[Force field (chemistry)|force field]], is crucial to the success of molecular mechanics calculations. A force field parameterized against a specific class of molecules, for instance, proteins, would be expected to only have any relevance when describing other molecules of the same class.<ref name="Ramachandran-2008" /> These methods can be applied to proteins and other large biological molecules, and allow studies of the approach and interaction (docking) of potential drug molecules.<ref>{{cite journal |url=http://www.bio-balance.com/JMGM_article.pdf |archive-url=https://web.archive.org/web/20080227144550/http://www.bio-balance.com/JMGM_article.pdf |archive-date=2008-02-27 |url-status=live|doi=10.1016/j.jmgm.2006.02.008|pmid=16574446|title=Molecular dynamics of a biophysical model for β2-adrenergic and G protein-coupled receptor activation|journal=Journal of Molecular Graphics and Modelling|volume=25|issue=4|pages=396–409|year=2006|last1=Rubenstein|first1=Lester A.|last2=Zauhar|first2=Randy J.|last3=Lanzara|first3=Richard G.|bibcode=2006JMGM...25..396R }}</ref><ref>{{cite journal |url=http://www.bio-balance.com/GPCR_Activation.pdf |archive-url=https://web.archive.org/web/20040530155723/http://bio-balance.com/GPCR_Activation.pdf |archive-date=2004-05-30 |url-status=live|doi=10.1016/S0166-1280(98)90217-2|title=Activation of G protein-coupled receptors entails cysteine modulation of agonist binding|journal=Journal of Molecular Structure: THEOCHEM|volume=430|pages=57–71|year=1998|last1=Rubenstein|first1=Lester A.|last2=Lanzara|first2=Richard G.}}</ref>[[File:A_molecular_dynamics_simulation_of_argon_gas.webm|thumb|Molecular Dynamics for Argon Gas]]