Computation of pressure components due to Class II force fields.

Area of Science:

• Computational chemistry
• Molecular dynamics simulations
• Biomembrane modeling

Background:

• Purely angle-dependent terms in force fields do not affect total simulation pressure.
• However, these terms, along with cross-terms like bond stretch, influence individual pressure tensor components.

Purpose of the Study:

• To demonstrate the straightforward computation of virial contributions to the pressure tensor.
• To investigate the role of cross-terms in Class II force fields, including bond stretch, angle, and torsional interactions.

Main Methods:

• Developing a method to compute virial contributions using bond distance vectors and atom forces.
• Applying the method to a Class II force field topology.
• Performing molecular dynamics simulations of a phospholipid biomembrane using the cff97 force field.

Main Results:

• Virial contributions to the pressure tensor are readily calculable using bond distance vectors and atom forces for Class II force fields.
• Angle and torsional cross-terms were found to make a substantial contribution to the pressure tensor in the phospholipid biomembrane simulation.

Conclusions:

• Cross-terms, specifically angle and torsional interactions, are crucial for accurately determining the pressure tensor in molecular simulations.
• The developed method provides an accessible way to compute these contributions, enhancing the accuracy of pressure calculations in complex systems like biomembranes.