Beyond point charges: novel electrostatic developments in force fields
CECAM-HQ-EPFL, Lausanne, Switzerland
Registration of contributed abstracts closed on 31st January 2016
Our CECAM workshop will address the known limitations of additive fixed point-charge electrostatics and discuss specifically when and how more sophisticated energy functions are best applied. It will bring together developers of these new physical models and users of the key simulation force fields (AMOEBA, CHARMM-DRUDE, SIBFA, NEMO, GEM, GROMOS) to answer these questions.
The workshop will address:
• The deficiencies of conventional fixed-charge force fields. The fixed-charge approximation has proved remarkably robust and successful, largely thanks to the many generations of effort in parameterisation. The purpose of this section is to identify clear cases where fixed-charge models fail and careful reparameterisation will not recover accuracy.
• The hierarchies of methodologies for moving beyond this approximation, including multipole-based methods and polarisable potentials (2 sessions). There are many ways of improving on the point-charge model, particularly in the force fields named above. The purpose of this section is to examine the available options, and to assess their relative merits in terms of accuracy and associated computational and parameterisation cost.
• Issues of parameterisation of advanced electrostatic models. This section will address how parameters that are robust, accurate and transferable may be derived, focusing particularly on how compatibility with other components of the underlying force field may be achieved.
• Issues of implementation of these advanced potential energy functions. Given a particular choice of physical representation of advanced electrostatics, say, for example, the use of inducible dipoles to capture explicit polarisation, the associated equations may be solved using different routes. In this example, simple optimisation or extended Lagrangian methods may be used. The purpose of this section is to examine the merits of alternative approaches, the underlying software currently used to deploy these models, and to focus on particular computational black-spots.
• Applications of these methods, in particular the contexts in which the expense of these new force fields is rewarded with improved scientific insight. The widespread adoption of more sophisticated models will require clear exemplar applications demonstrating how the improved accuracy they achieve offsets the associated computational cost. This section will explore existing applications and propose new ideas, with particular reference to the deficiencies of fixed point-charge models discussed in the first session.
We propose to hold six half-day sessions organised around these topics, with introductory and summary talks. Our intention is to reach conclusions regarding what level of electrostatic model is appropriate for a particular problem, and how it may be best implemented and parameterised. To that end, the identified key workers in the sessions will lead discussion based on their ‘hands-on’ experiences of their own methodology development, applications and results. To allow diverse insights while being small enough to encourage discussion, we anticipate approximately 30 participants to attend.
Jean-Philip PIQUEMAL (Sorbonne Université) - Organiser & speaker
Thomas Simonson (Ecole Polytechnique, Palaiseau) - Organiser & speaker
Richard Bradshaw (University of Southampton) - Organiser & speaker
Jonathan Essex (University of Southampton) - Organiser