Dear all, I am having an interesting dihedral problem which is giving me a lot of trouble. Let me explain.
About some time ago, I equilibrated a system to run nve simulations. The last step for that equilibration is given below. Please note that pressure and dihedral values. I used setting lj/coul 0 0 1. Here I was using an old version of Jan 9, 2009.
---------------- Step 140160 ----- CPU = 49938.7675 (sec) ----------------
TotEng = 80205.2346 KinEng = 27563.5497 Temp = 300.5981
PotEng = 52641.6849 E_bond = 16991.9813 E_angle = 15002.7855
E_dihed = 16910.3186 E_impro = 147.9991 E_vdwl = -2960.6385
E_coul = 44059.3724 E_long = -44949.7777 Press = -33.6011
Now, I used the restart file created by above simulation and tried to run using latest (3 Nov version). To my surprise, I find that dihedral values are changed for the same timestep and geometry. (which changes overall pressure also). All others are exactly similar. Please see below.
---------------- Step 140160 ----- CPU = 0.0000 (sec) ----------------
TotEng = 80205.2346 KinEng = 27563.5497 Temp = 300.5981
PotEng = 52641.6849 E_bond = 16991.9813 E_angle = 15002.7855
E_dihed = 32131.3013 E_impro = 147.9991 E_vdwl = -2960.6385
E_coul = 44059.3724 E_long = -44949.7777 Press = 768.3282
More surprisingly, using the latest version, when I ran it on a different machine, I get different values for the dihedral. Please see below.
---------------- Step 140160 ----- CPU = 0.0000 (sec) ----------------
TotEng = 80205.2346 KinEng = 27563.5497 Temp = 300.5981
PotEng = 52641.6849 E_bond = 16991.9813 E_angle = 15002.7855
E_dihed = 24349.9629 E_impro = 147.9991 E_vdwl = -2960.6385
E_coul = 44059.3724 E_long = -44949.7777 Press = 451.3653
I am not sure what might be causing this problem. Restartfile reading? When I converted the rst file to datafile and ran the simulation, it resulted in the same answers in both cases. I also looked at the dihedral coefficients (in the datafile, just to be sure), they are same.
When I tried to run the same file older version (lammps 22 May 2008), it gave
---------------- Step 140160 ----- CPU = 0.0000 (sec) ----------------
TotEng = 72765.5902 KinEng = 27563.5497 Temp = 300.5981
PotEng = 45202.0406 E_bond = 16991.9813 E_angle = 15002.7855
E_dihed = 16910.3186 E_impro = 147.9991 E_vdwl = -2960.6386
E_coul = 44059.3724 E_long = -44949.7777 Press = -33.6011