[CPMD-list] RMS gradient

[Juerg Hutter]

Hi

> Dear Prof Hutter,
> Many many thanks for your clarification. Still I want
> to ask is this procedure is applicable during both
> the Geometry Optimization abd Molecular Dynamics
> scheme.If I am right, then this convergence can be
> checked from GNMAX/GEMAX values from output file.
> Suppose I want to get a optimized structure (Roughly)
> of pyridine dimer by Geometry Optimization(First
> method) and by ab Molecular Dynamics simulation(Second
> methos). Then can I confirm the convergence by just
> looking at GNMAX/GEMAX values. Which way will be
> better to get a optimized geometry i.e. by only
> OPTIMIZE GEOMETRY or MOLECULAR DYNAMIC or BOTH.

If you optimize a structure with MD (using ANNEALING)
you have to investigate the gradients yourself or
you can add a single step of optimization and print out the
gradient with the RMS and Max. abs error.

regards

Juerg Hutter


>
> Thanks again,
> keta
>
> --- Juerg Hutter <hutter at pci.unizh.ch> wrote:
>
> > Hi
> >
> > The root mean square
> > (see
> > http://mathworld.wolfram.com/Root-Mean-Square.html)
> > is a measure for the size of a distribution. We use
> > it
> > to give a size of the electronic gradient during the
> > minimization. The optimized energy is found for
> > the case of zero gradient. Numerically this is
> > monitored
> > by the RMS value of the gradient.
> > However, there is a second measure, the largest
> > absolute
> > value of an element of the gradient.
> > In CPMD both measures are printed, side by side in
> > the
> > output. Convergence is checked wrt the largest
> > gradient
> > element. Convergence is assumed if this value
> > falls below a threshold (default 10^-5).
> >
> > regards
> >
> > Juerg Hutter
> >
> >
> ----------------------------------------------------------
> > Juerg Hutter                   Phone : ++41 1 635
> > 4491
> > Physical Chemistry Institute   FAX   : ++41 1 635
> > 6838
> > University of Zurich           E-mail:
> > hutter at pci.unizh.ch
> > Winterthurerstrasse 190
> > CH-8057 Zurich, Switzerland
> >
> ----------------------------------------------------------
> >
> >
> > On Tue, 25 Jan 2005, Keta Jones wrote:
> >
> > > Please help me to explain the significance of
> > "Root
> > > mean square gradient" for energy minimization of
> > > systems.How can I check this from CPMD output file
> > ?
> > >
> > > regards
> > > keta
> > >
> > > =====
> > > Keta
> > >
> >
> **************************************************************************************
> > >
> > >
> > >
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