Degrees of Freedom

Overview

Teaching: 10 min
Exercises: 0 min
Questions
  • How is kinetic energy contained and distributed in a dynamic molecular system

  • How to increase efficiency of thermodynamic sampling

  • How reduction of degrees of freedom affects dynamics

Objectives
  • Explain how kinetic energy is distributed in a simulation system

  • Understand how to correctly increase efficiency of thermodynamic sampling

Molecular degrees of freedom

Equipartition theorem

Degrees of freedom and thermodynamics properties

Translational degrees of freedom

Rotational degrees of freedom

Vibrational degrees of freedom

Angle bend Symmetric stretch Asymmetric stretch
bend symmetric asymmetric

Increasing efficiency of thermodynamic sampling.

By reducing the number of degrees of freedom we can increase thermodynamic sampling efficiency.

Reduction of the number of degrees of freedom may lead to artifacts.

Bond and angle constraints can:

Key Points

  • Constraints decrease the number of degrees of freedom

  • Imposing constraints can affect simulation outcome