[gmx-users] TI problem: When Lambda is 0/1, Trun on/off soft core potential get different result

[jia jia]

Dear all:
   I just test the tutrial (
http://www.dillgroup.ucsf.edu/group/wiki/index.php/Free_Energy:_Tutorial)
and my own system, and I fond somthing confused me: If I understand correct,
when lamda is 0 (all atoms on), there should be no difference between trun
on or turn off soft-core potentional. In addition, there should be no
different whatever you set the sc-alpha value.
    However, I've test the methane system on both gromacs 4.0.4 and 3.3.3,
and found when lamda is 0, you get different large result when sc-alpha were
set to 0, 0.5 and 1.5.
   I wonder has any one notice this before or I misunderstood the formula?

 Yours
Jia
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