Compute fep-work of adhesion

Dear lammps users and developers,

I’m trying to use fix/adapt and compute/fep commands to get the work of adhesion between water and metallic substrates.

This is the fep part of the script:
1 is Ge, 3 is Ow. Lj with lj/cut between the two.

variable lambda equal ramp(1.0,0.0)
variable dlambda equal -0.05
variable epsilon equal 0.0074437*v_lambda

variable Nadapt equal 100000
variable Nevery equal 40
variable Nrepeat equal 2000

fix ADAPT all adapt/fep {Nadapt} pair lj/cut epsilon 1 3 v_epsilon & after yes fix PRINT all print {Nadapt} "adapt lambda = {lambda} epsilon={epsilon} "

compute FEP all fep 298.15 pair lj/cut epsilon 1 3 v_epsilon

fix FEPAVE all ave/time {Nevery} {Nrepeat} ${Nadapt} c_FEP[1] c_FEP[2] file fep_solo_10_400fep.lmp

The output of the fep is like:


Which sums up to -19.6 eV–>577 mj/m^2 of work of adhesion, definitely too much.

Am i missing something in the post-interpretation or in the command?
input file and fep output attached

Any hints would be appreciated.

fep_1.lmp (595 Bytes)

in_1.lmp (3.07 KB)