CHARMM Development Project
Posted By: lin1209 EHFCor in vacuum simulation - 06/24/20 06:15 AM
I am using the DYNA VV2 integrator with thermostats (TPCONTROL) to run vacuum simulations with both Drude and additive FF.
The EHFCor (high frequency correction) has a value is 1.3 kcal for additive FF and -8.83 for Drude FF.
The values seem too large, does this mean there's something wrong with my simulation or is this normal when using VV2?
I read in this post: saying that EHFCor also has energy content for heat bath when using VV2.
Should I include this term when I want to use the potential or should I just use the potential printed out (ENERgy), that is whenever I need E_pot should I use the value of ENERgy+EHFCor or just ENERgy?

Here's my inp when running the vacuum simulation with additive FF:
the system only contains one molecule and no pbc was set.

set cutoff 999
set ctofnb = @cutoff
Calc ctofnb = @ctofnb - 2.0
set ctonnb = @ctofnb
Calc ctonnb = @ctonnb - 1.0

! shake constraint
SHAKE bonh param nofast -
select .not. type D* end -
select .not. type D* end

set seed 314159

MINI SD nstep 100 nprint 50 -
atom vatom vdistance cdie eps 1.0 vswitch fshift wmin 1.2 -
cutnb @cutoff ctofnb @ctofnb ctonnb @ctonnb -
e14fac 0.0

tpcontrol nther 1 nstep 1 -
ther 1 tau 0.1 tref @temp select all end -

set NSTEPS = 100000000
set printfreq = 1000
OPEN WRITE CARD UNIT 62 NAME gas.nose ! info for temperaature
open unit 35 write form name gas.rst ! restart file
open unit 32 write unfo name gas.trj ! trajectory
open unit 33 write form name gas.kunit ! Temperature
open unit 34 write unfo name gas.vel ! velocity

DYNA vv2 start -
nstep @NSTEPS time 0.001 -
iunread -1 -
iunwrite 35 iuncrd 32 iunvel 34 kunit 33 -
nsavc @printfreq nsavv @printfreq nprint @printfreq isvfrq @printfreq -
iprfrq @NSTEPS ntrfrq @NSTEPS - ! what's used for swm4 water
cutnb @cutoff ctofnb @ctofnb ctonnb @ctonnb -
firstt @temp -
finalt @temp -
iasvel 1 iseed 314159 -
iuno 62 nsnos @printfreq

Thanks in advance!
© CHARMM forums