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Updated: Jul 14, 2026
07:31
Realistic Membrane Modeling Using Complex Lipid Mixtures in Simulation Studies
Published on: September 1, 2023
Free energy calculations using flexible-constrained, hard-constrained and non-constrained molecular dynamics
Markus Christen1, Clara D Christ, Wilfred F van Gunsteren
1Laboratory of Physical Chemistry, Swiss Federal Institute of Technology, ETH, 8093 Zürich, Switzerland.
Summary
Different treatments for bond-stretching in molecular dynamics simulations impact results. Flexible constraints offer a balance, showing smaller variations in free energy and density compared to rigid or fully flexible bonds.
Area of Science:
- Computational Chemistry
- Molecular Dynamics Simulations
- Thermodynamics
Background:
- Accurate molecular dynamics simulations require precise handling of molecular constraints.
- Varying methods for bond stretching can influence simulation outcomes.
Purpose of the Study:
- To compare the effects of different bond treatments (rigid, partially rigid, flexible) on molecular dynamics simulations.
- To analyze the impact of these treatments on free energy calculations.
Main Methods:
- Utilized multi-configurational thermodynamic integration to simulate the transformation of water to methanol.
- Employed SHAKE algorithm for rigid bonds and a flexible constraints algorithm for partially rigid bonds.
- Compared simulations with fully flexible bonds against constrained methods.
Main Results:
- Differences in bond treatments led to up to 2% variation in liquid densities.
- (Excess) free energy differences of up to 5.7 (4.3) kJ mol(-1) were observed due to bond treatments.
- These variations were smaller than differences arising from distinct water/methanol models.
Conclusions:
- The choice of bond constraint method in molecular dynamics simulations affects calculated properties.
- Flexible constraints provide a viable alternative, balancing computational efficiency and accuracy.
- Model differences have a more significant impact on free energy and density than bond constraint methods.
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