[gmx-users] BAR gives different result than TI

[David van der Spoel]

Hi,

we've been trying to do free energy calculations for solvation of two 
small molecules in water, n-butylamine (NBA) and diethyl-ether (DEE). 
For one of them the result with BAR (using Justin's tutorial) is 
significantly different from TI:
       BAR     TI      Exper. (kJ/mol)
NBA   -11.1   -10.8   -17.9
DEE   -11.0   -1.8     -7.4

Since for NBA the results are pretty close it seems that the protocol 
should be right, and the numbers seem to have converged pretty good as well.

Any clues why these results could be so different?

-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se