Common Approximations in Molecular Models

• Rigid intramolecular degrees of freedom

  • fast intramolecular motions slow down MD calculations

• Ignore hydrogen atoms

  • united atom representation

• Ignore polarization

  • expensive n-body effect

• Ignore electrostatics

• Treat whole molecule as one big atom

  • maybe anisotropic

• Model vdW forces via discontinuous potentials

• Ignore all attraction

• Model space as a lattice

  • especially useful for polymer molecules

Qualitative models

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