equilibrate the bulk water system

From: Hasan haska (hasanhaska_at_yahoo.com)
Date: Tue Mar 10 2015 - 16:51:30 CDT

DearNAMD users,

 
Iwant to minimize and equilibrate a bulk water system that includes 7048water molecules (SPC/E water model) in a rectangular box with the d=0.996 g/cm3experimental density at 300K. Therefore I prepared a namd conf file belowand started to run it. But after minimization was completed I got the error,which is in below. My aim is to run minimization and NPT simulation withkeeping the dimension of the unit cell in the x-y plane constant while allowingfluctuations along the z axis in order to get the real cell sizes ( 55 X 55 X70 Angs ) according to the density. Then run a NVT simulation with these cellsize. How can I solve this problem ?  Could you please share your opinionand experience ?

 

 
Thanks.

 

 
http://www.filedropper.com/water_1

 
My simulation files are in the linkabove.

 

 
*****************************

Error:

------------- Processor 0 Exiting:Called CmiAbort ------------

Reason: FATAL ERROR: Stray PME gridcharges detected!

 
FATAL ERROR: Seehttp://www.ks.uiuc.edu/Research/namd/bugreport.html

 
Charm++ fatal error:

FATAL ERROR: Stray PME grid chargesdetected!

 
**************************

 

 
#--- This is a test namd configurationfile

#############################################################

## 

#############################################################

 

paratypeCharmm  on

parameters    water.PRM

 

structure             water.psf  #

coordinates           water_.pdb  #

outputName            water_1out  #

 

set temperature    300

  

temperature $temperature

                  

firsttimestep     0

 

# Integrator Parameters

timestep           1.0

nonbondedFreq      2

fullElectFrequency 4    

stepspercycle      16  

 

 

# Force-Field Parameters

exclude        scaled1-4 

1-4scaling     1.0

cutoff         18.

switching      on

switchdist     15.            

pairlistdist    20.

 

 

# Constant Temperature Control

langevin           on   ;# do langevin dynamics

langevinDamping    1    ;# damping coefficient (gamma) of 5/ps

langevinTemp       $temperature

langevinHydrogen   on    ;#  couple langevin bath to hydrogens

 
 
# Constant Pressure Control (variablevolume)

 

useGroupPressure     no ;# needed for 2fs steps

useFlexibleCell      yes  ;# no for water box, yes for membrane

useConstantArea      yes  ;# no for water box, yes for membrane

 

langevinPiston       on

langevinPistonTarget  1.01325;#  in bar -> 1 atm

langevinPistonPeriod  200.

langevinPistonDecay   50.

langevinPistonTemp   $temperature

 

 #--- PBC

 

cellBasisVector1  55.0  0.0    0.0

cellBasisVector2   0.0 55.0    0.0

cellBasisVector3  0.0   0.0  100.0

 

 
#--- PME 

PME                yes

PMEGridSpacing     1.0

  

#--- Output & Restart

 

binaryoutput    no

 

binaryrestart   yes

 

restartname    water_1restart      #

DCDfile        water_1out.dcd      #

 

restartfreq       5000      #

dcdfreq           5000

xstFreq           5000

outputEnergies    5000

outputPressure    5000

outputtiming      5000

 

minimize 10000

reinitvels         $temperature

run 10000000

# 10 ns 2002 record

 

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