Hi,

Is it normal to see positive value of VDW energy in traj?

My MD traj result seems OK, and total energy fluctuates around a constant value, but the VDW energy always be a positive number, while the ELEC energy is a much bigger minus number, so the total energy is still minus.

I set up my MD NVT running with:

nbond inbfrq -1 imgfrq -1 atom vatom cdie eps 1.0 -
elec ewald pmew fftx 48 ffty 48 fftz 48 kappa .34 spline order 6 -
vdw vswitch cutnb 14.0 cutim 14.0 ctofnb 12. ctonnb 10. wmin 1.0

scalar mass stat
set pmass 0
calc tmass = int( ?stot / 50.0 ) * 5
dyna leap cpt restart - !
timestep 0.001 nstep 20000 nprint 10000 iprfq 2000 - !
iunrea 51 iunwri 41 iuncrd 31 nsavcc 1 - !
hoover reft @tk tmass @tmass tbat @tk firs @tk tstr @tk - !
pcons pmzz @pmass pmxx 0.0 pmyy 0.0 pref 1.0 - !
pint pref 1.0 pgamma 0.0 - !
ihtfrq 0 ieqfrq 0 ntrfrq 50 - !
iasors 1 iasvel 1 iscvel 0 ichecw 0 - !
ixtf 1000 echeck 100. !

Is that make sense or I set something wrong?

Also, I pick some clusters out and calculate energy of them, without PME set, the VDW energy shows a great number about xx+E066, and ELEC energy seems OK but can no longer balance the total energy to a reasonable value, why?

Thanks for any kindly help