[gmx-users] Charmm foce field and free energy
fileti at gmail.com
Sun Jul 8 02:47:44 CEST 2012
I'm trying to reproduce the hydration free energy of the methanol using
the CHARMM force field. However I am getting a value considerably
lower than the experimental: 17 kJ mol-1 (the experimental value is 21
Am I forgetting some technicality related to the force field?
I using a detailed thermodynamic integration procedure, where I decouple
Couloumb and van der Waals interactions separately, at lambda
intervals of 0.04.
I'm using sd integrator and softcore to decouple van der Waals interactions.
NPT, box with 1000 TIP3P water molecules and one methanol molecule,
400ps per window.
In a general review I noticed that is not easy to obtain good
accuracies in this property.
For example, the original paper (J Comput Chem 29: 2543, 2008), is reported a
overestimated value of 23.9 kJ mol-1. In J Phys Chem B 110: 17616,
2006, Hess got a underestimated result
by 2 kJ mol-1. Shits reported a value of 18.87 kJ mol-1 in J Chem Phys
122: 134508, 2005.
These inexact values is inherent to the models or there was any way to improve
the accuracy through the protocol used?
Eudes Eterno Fileti
Instituto de Ciência e Tecnologia da UNIFESP
Rua Talim, 330, São José dos Campos - SP
Tel.: (12) 3309-9573
More information about the gromacs.org_gmx-users