[CPMD-list] More on NOSE Electrons..

[Juerg Hutter]

Hi

> Thank you, Christl, for pointing out the Blochl and Parrinello (1992,
> PRB, 45:9413) paper to me.
>
> As I understand it, for the long simulations I'm trying (~ 5 ps), I
> certainly want to thermostat the fictitious kinetic
> energy of the electronic wavefunctions.  Blochl and Parrinello point
> out that periodic quenching to the BO surface will screw up the
> dynamics unless you do it at every timestep.
>
> In equation 6 of the Blochl and Parrinello (1992; PRB) paper, they
> suggest  the target fictitious kinetic energy of the electronic wave
> functions to be
>
> 		2kbT(mu/M) SUM<psi |-1/2del2 | psi>
>
> where, as I see it, the summation (SUM<psi |-1/2del2 | psi>) is simply
> the total real electronic kinetic energy in the ground state (in A.U),
> mu is the fictitious mass of the wavefunction, and M is the mass of one
> atom.    However, since kbT has units of energy, then the whole
> expression  has units of energy**2.  This can't be right; is there a
> typo or am  I confused about something..?

This is the "beauty" of atomic units. The sum in the formula is the
electronic kinetic energy, but only in atomic units. If you use
another system there would be some constants with appropriate units.
Please also notice that mu hasn't simply units of a mass!

regards

Juerg Hutter


>
> Thanks for your help!
>
> Dave Sherman
> ______________
> David M. Sherman
> Professor of Geochemistry
> Department of Earth Sciences
> University of Bristol
> Bristol BS8 1RJ UNITED KINGDOM
> Phone: 44-(0)117-954-5446
> http://mineral.gly.bris.ac.uk
>
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