Hello,
I have a strange problem with a 100 molecule system where I used cut-
off electrostatics and I want to use pme from now.
After md with Coulomb cut-off, I minimised with steep (and the same
Coulomb cut-off) and it ends OK:
Step= 395, Dmax= 1.7e-06 nm, Epot= -5.04260e+04 Fmax= 1.15989e+02,
atom= 4130
Step= 396, Dmax= 2.0e-06 nm, Epot= -5.04045e+04 Fmax= 1.15977e+02,
atom= 4130
Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1
Double precision normally gives you higher accuracy.
writing lowest energy coordinates.
Steepest Descents converged to machine precision in 397 steps,
but did not reach the requested Fmax < 1.
Potential Energy = -5.0425977e+04
Maximum force = 1.1598901e+02 on atom 4130
Norm of force = 1.6355400e+03
I take this minimised .gro and I minimise it again but now I change
to PME electrostatics. It crashes from the beginning with an infinite
force (not on the atom with the previous maximum force) and the
energy is huge: 6.56504e+19 instead of -5.0425977e+04 which was the
end of the previous minimisation. Do you have any explanation? Should
I change some PME parameters?
Step= 0, Dmax= 1.0e-02 nm, Epot= 6.56504e+19 Fmax= inf,
atom= 164
Step= 14, Dmax= 1.2e-06 nm, Epot= 6.56504e+19 Fmax= inf,
atom= 164
Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1
Double precision normally gives you higher accuracy.
writing lowest energy coordinates.
Steepest Descents converged to machine precision in 15 steps,
but did not reach the requested Fmax < 1.
Potential Energy = 6.5650353e+19
Maximum force = inf on atom 164
Norm of force = inf
Thanks for any advice,
Ioannis
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