Free energy calculations, soft-core potential - Redmine #2601
Archive from user: Vytautas Gapsys
Current Gromacs implementation of the soft-core potential for free energy calculations implements a version described by Beutler et al, 1994. Potential of this form has been shown to suffer from undesired minima along the alchemical path when van der Waals and electrostatic interactions are switched simultaneously. For certain free energy calculation protocols, e.g. discrete TI, BAR, a workaround of separate switching of the electrostatic and van der Waals interactions has become a standard practice. For the single topology alchemical methods, however, such an approach introduces the requirement of generating several separate topologies. Also, for different free energy calculation protocols, e.g. non-equilibrium methods, performing non-bonded interaction switching simultaneously is more practical.
To alleviate the problems of the current soft-core potential and allow
for a simultaneous Coulombic and van der Waals switching, an alternative
formulation of the potential was proposed
https://dx.doi.org/10.1021/ct300220p
The new soft-core version sets the force to a finite value between the
alchemically transformed particles at short distances. In contrast to
the Beutler et al, 1994 soft-core, this finite, but small force allows
avoiding the unwanted minima along the transition path. The new
soft-core version has been implemented in Gromacs 4.6.2 and extensively
tested by calculating free energy changes for the amino acid, nucleic
acid and ligand modifications.
The current aim is to incorporate the new soft-core version into the Gromacs master branch. The new function will not replace the current soft-core implementation, but allow the user to choose between the soft-core versions.
People involved in implementation: Luka Stanisic, Vytautas Gapsys, Carsten Kutzner, Markus Rampp, Bert de Groot
(from redmine: issue id 2601, created on 2018-08-08 by gmxdefault)
- Relations:
- relates #742 (closed)
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