Sai Pooja wrote:
Hi,
I am trying to reproduce results from a paper which uses this cutoff.
The work is on loop-folding and they use implicit solvent. I am using
explicit solvent with charmm 27. Below is my mdp file. I am not sure if
there is any advantage in using a large cut-off.
Large cutoffs can cause artifacts. This .mdp file also does not match the error
message you quoted before. If it is indeed accurate, then it looks like your
.mdp file is being interpreted incorrectly (2.0-nm cutoffs instead of 1.8 nm).
If there is a misinterpretation, file a bugzilla. If you've simply posted the
wrong file, please post the correct file, if necessary. But I'd suggest you do
some homework about the effects of long cutoffs, especially if they deviate from
what the force field derivation requires.
-Justin
; VARIOUS PREPROCESSING OPTIONS
title = NVT simulation (constant number, pressure and
temperature)
cpp = /lib/cpp
define =-DPOSRES
; RUN CONTROL PARAMETERS
integrator = md
dt = 0.002
nsteps = 100000
; OUTPUT CONTROL OPTIONS
nstxout = 10000
nstvout = 0
nstfout = 0
nstlog = 10000
nstenergy = 10000
nstxtcout = 0
xtc_precision = 0
xtc-grps = System
energygrps = Protein Non-Protein
; NEIGHBORSEARCHING PARAMETERS
nstlist = 5
ns-type = Grid
pbc = xyz
rlist = 1.8
; OPTIONS FOR ELECTROSTATICS AND VDW
coulombtype = PME
fourierspacing = 0.12
rcoulomb = 1.8
epsilon_rf = 78
vdw-type = Cut-off
rvdw = 1.8
; FFT grid size, when a value is 0 fourierspacing will be used =
fourier_nx = 0
fourier_ny = 0
fourier_nz = 0
; EWALD/PME/PPPM parameters =
pme_order = 4
ewald_rtol = 1e-05
epsilon_surface = 0
optimize_fft = no
; Temperature coupling
Tcoupl = Berendsen
tc-grps = Protein Non-Protein
tau_t = 0.2 0.2
ref_t = 300 300
; Pressure coupling
Pcoupl = Berendsen
Pcoupltype = Isotropic
tau_p = 1.0
compressibility = 4.5e-5
ref_p = 1.0
; GENERATE VELOCITIES FOR STARTUP RUN
gen_vel = no ; Assign velocities to particles by
taking them randomly from a Maxwell distribution
gen_temp = 300.0 ; Temperature to generate
corresponding Maxwell distribution
gen_seed = 9999 ; Seed for (semi) random number
generation.
; OPTIONS
constraints = all-bonds
Pooja
On Fri, Jul 16, 2010 at 8:22 PM, Justin A. Lemkul <jalem...@vt.edu
<mailto:jalem...@vt.edu>> wrote:
Sai Pooja wrote:
Hi,
I am getting these notes when I run grompp:
NOTE 3 [file Init/ffsb_init.top]:
The largest charge group contains 12 atoms.
Since atoms only see each other when the centers of geometry of
the charge
groups they belong to are within the cut-off distance, too
large charge
groups can lead to serious cut-off artifacts.
For efficiency and accuracy, charge group should consist of a
few atoms.
For all-atom force fields use: CH3, CH2, CH, NH2, NH, OH, CO2,
CO, etc.
initialising group options...
processing index file...
Analysing residue names:
There are: 3484 OTHER residues
There are: 67 PROTEIN residues
There are: 0 DNA residues
There are: 0 RNA residues
Analysing Protein...
Analysing Other...
Making dummy/rest group for Acceleration containing 11343 elements
Making dummy/rest group for Freeze containing 11343 elements
Making dummy/rest group for VCM containing 11343 elements
Number of degrees of freedom in T-Coupling group Protein is 1777.76
Number of degrees of freedom in T-Coupling group non-Protein is
20898.23
Making dummy/rest group for User1 containing 11343 elements
Making dummy/rest group for User2 containing 11343 elements
Making dummy/rest group for XTC containing 10450 elements
Making dummy/rest group for Or. Res. Fit containing 11343 elements
Making dummy/rest group for QMMM containing 11343 elements
T-Coupling has 2 element(s): Protein non-Protein
Energy Mon. has 2 element(s): Protein non-Protein
Acceleration has 1 element(s): rest
Freeze has 1 element(s): rest
User1 has 1 element(s): rest
User2 has 1 element(s): rest
VCM has 1 element(s): rest
XTC has 2 element(s): Protein rest
Or. Res. Fit has 1 element(s): rest
QMMM has 1 element(s): rest
Checking consistency between energy and charge groups...
Largest charge group radii for Van der Waals: 0.288, 0.263 nm
Largest charge group radii for Coulomb: 0.288, 0.263 nm
NOTE 4 [file nvtp.mdp]:
The sum of the two largest charge group radii (0.551009) is
larger than
rlist (2.000000) - rvdw (2.000000)
Can someone tell me how to correct these?
Note 3 is explained in detail in the error message. Beyond that,
read about the group concept in the manual.
I've never seen Note 4 before, but a 2-nm cutoff is a bit strange
for a protein simulation. Any reason you're using such large
cutoffs? You may also want to provide your whole .mdp file to see
if anyone can spot the underlying issue.
-Justin
--
========================================
Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu <http://vt.edu> | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
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--
========================================
Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
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