[gmx-users] energy minimization using double precision gromacs failed
sansanqin00 at mails.tsinghua.edu.cn
Mon Aug 13 11:08:34 CEST 2007
Hello, gmx-users,I tried to energy minimize a lipidbilayer consisting of
32 lipids(16 up and 16 down) with two water layers(428 up and 428 down).
my em.mdp is like this:
cpp = /lib/cpp
define = -DFLEXIBLE
constraints = none ;h-bonds
lincs_iter = 4
; RUN CONTROL PARAMETERS =
integrator = l-bfgs
tinit = 0
dt = 0.2 ; ps
nsteps = 6000
nstxtcout = 100 ; pos to xtc file
nstlist = 5
ns_type = grid
rlist = 0.7
coulombtype = PME
rcoulomb = 0.7
vdw-type = Cut-off
rvdw = 0.7
fourierspacing = 0.095 ; default to 0.12
fourier_nx = 0
fourier_ny = 0
fourier_nz = 0
pme_order = 4
ewald_rtol = 1e-5
optimize_fft = yes
; ENERGY MINIMIZATION OPTIONS =
emtol = 0.00001 ; default to 100
emstep = 0.5 ; default to 0.01
nstcgsteep = 1000
The em is done using double-precision gromacs program,and the out put is
Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1e-05
writing lowest energy coordinates.
Low-Memory BFGS Minimizer converged to machine precision in 7 steps,
but did not reach the requested Fmax < 1e-05.
Potential Energy = 1.25811048952284e+15
Maximum force = 5.23956606456297e+17 on atom 483
Norm of force = 6.77707038974525e+15
How can I prevent it from converging to machine precision? Is there any
method to change the standard of machine precision?
Any suggestion will be appreciated , thanks a lot.
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