[gmx-users] error in calculating free energy of solvation

Justin Lemkul jalemkul at vt.edu
Tue Feb 12 14:31:10 CET 2019

On 2/12/19 3:34 AM, daniel madulu shadrack wrote:
> Hi all,
> I am calculating the free energy of solvation in gromacs but I get this
> error, please help, I have tried all the options without sucdcess.
> Fatal error:
> There is no path between the states X & Y below that is covered by foreign
> lambdas:
> cannot proceed with BAR.
> Use thermodynamic integration of dH/dl by calculating the averages of dH/dl
> with g_analyze and integrating them.
> Alternatively, use the -extp option if (and only if) the Hamiltonian
> depends linearly on lambda, which is NOT normally the case.
> lambda vector [X]:  init-lambda-state=3 (mass-lambda) l=0 (coul-lambda) l=0
> (vdw-lambda) l=0.15 (bonded-lambda) l=0 (restraint-lambda) l=0
> lambda vector [Y]:  init-lambda-state=5 (mass-lambda) l=0 (coul-lambda) l=0
> (vdw-lambda) l=0.25 (bonded-lambda) l=0 (restraint-lambda) l=0

Looks like you're missing lambda state 4 between these two. Make sure 
you're providing all relevant data files to gmx bar.



Justin A. Lemkul, Ph.D.
Assistant Professor
Office: 301 Fralin Hall
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Virginia Tech Department of Biochemistry
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jalemkul at vt.edu | (540) 231-3129


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