FreeEnergy: Not enough steps to complete pfm & mcti blocks

From: priyodorshi satpati (psatpati_at_gmail.com)
Date: Wed Nov 25 2009 - 09:31:15 CST

Dear all,

I was trying to run a 100ps restraint-distance simulation. My input is given
below :

***************************
paraTypeCharmm on
parameters par_satpati_gdp_hpo4.prm

exclude scaled1-4
1-4scaling 1.0
switching on

cutoff 16.
switchdist 15.

pairlistdist 18.
stepspercycle 10
timestep 2.0
nonbondedFreq 1
fullElectFrequency 2

#Harmonic restraint parameters
rigidBonds all
rigidTolerance 1.0e-8

# periodic cell
cellBasisVector1 51.5 0 0
cellBasisVector2 0 51.1 0
cellBasisVector3 0 0 51.1
cellOrigin -0.13 0.03 0.01
extendedSystem $inputname.xsc
wrapAll on

# full electrostatics
PME on
PMEGridSizeX 75
PMEGridSizeY 75
PMEGridSizeZ 75

# Constant Temperature Control
langevin on
langevinDamping 5
langevinTemp $temperature
langevinHydrogen off

# pressure control
useGroupPressure yes
useFlexibleCell no
useConstantArea no
langevinPiston on
langevinPistonTarget 1.01325
langevinPistonPeriod 200.
langevinPistonDecay 100.
langevinPistonTemp $temperature

#output files
binaryoutput no
outputName $outputname ;# base name for output from this run
restartfreq 50 ;# 50 steps = every 0.1ps
dcdfreq 100
xstFreq 100
outputEnergies 100 ;# 100 steps = every 0.2 ps

freeEnergy on
freeEnergyConfig {
urestraint {

dist (LIGA,1,P1) (LIG2,2,MG) kf=20 ref=2.63

}

pmf {
    task = stop
    time = 100 ps
  }

}
***************************************************************

but I got the following error :

Info: RELATIVE IMPRECISION IN VDWA TABLE ENERGY: 2.06776e-20 AT 21.9986
Info: FREE ENERGY PERTURBATION CONFIG
Info: ***********************************

urestraint {

dist (LIGA,1,P1) (LIG2,2,MG) kf=20 ref=2.63

}

pmf {
    task = stop
    time = 100 ps
  }

Info: ***********************************
FreeEnergy: Not enough steps to complete pfm & mcti blocks
FreeEnergy: Num Steps Needed = 50001
FreeEnergy: Num Steps Requested = 0
FATAL ERROR: FreeEnergy: Fatal Run-Time Error
Stack Traceback:
  [0] CmiAbort+0x20 [0x8ca446]
  [1] _Z8NAMD_diePKc+0x65 [0x4bcf25]
  [2] _ZN22GlobalMasterFreeEnergy15user_initializeEv+0x1e7 [0x702541]

please let me know what should i do to overcome this problem.

regards and best wishes

satpati

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