Question about Ryckaert-Belleman torsion

The functionality of OpenMM will (eventually) include everything that one would need to run modern molecular simulation.
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Siddharth Srinivasan
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Question about Ryckaert-Belleman torsion

Post by Siddharth Srinivasan » Mon Jul 06, 2009 3:42 pm

The AMBER forcefield equations that we use have the same functional form as the PeriodicTorsionForce implementation in OpenMM. The improper torsion term is exactly the same, and I can incorporate it pretty easily. For proper torsions, we have the additional "multiplicity" variable with different parameters of barrier height and phase for each instance, the functional form is the same, except with a summation over the "multiplicity". In order to get the same effect from OpenMM, would I simply call PeriodicTorsionForce multiple times for each proper torsion (to emulate the multiplicity for each proper torsion), or would I need to use the RBTorsionForce somehow?
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Michael Sherman
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RE: Question about Ryckaert-Belleman torsion

Post by Michael Sherman » Tue Jul 07, 2009 10:54 am

Hi, Sid. I believe you just need multiple calls to PeriodicTorsionForce. Regards, Sherm
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