R*Kmax for different RMTs [Re: [Wien] (no subject)]

[Dr.R.S.Rao]

Dear Wien users and Steven:
	We have tested by keeping RMT*KMAX constant also. There is almost
same result regarding the relative stability of structures. Very little
change in terms of energy differences per atom. The problem is that
relative stability of orthorhombic and AlB_2 type depend on the chosen
RMT and the energy differences are not negligible : about 5-10 mRy per
atom. To reach hihger compressions we have to reduce RMT so that plane
wave cut-off at different compressions remain same.
	So how to rely on the results? Generally it is preferable to make
RMT as large as possible, but we want to go for higher compression and
keep plane wave cut-off constant.
	Please advice.
Thanking you
Ashok
On Sat, 22 Nov 2003, Steven Homolya wrote:

>
> Problem is that you have adjusted RMT*Kmax to keep Kmax constant. For a
> meaningful comparison, keep RMT*Kmax the same, regardless of the value of
> RMT. The smaller the RMT, the more plane waves you need, i.e., greater
> Kmax (prop. to RMT^-1). This is why WIEN takes RMT*Kmax as an input
> variable, and not Kmax.
>
> On Fri, 21 Nov 2003, Ashok Kumar Verma wrote:
>
> > Dear wien users,
> >
> >                   I am having one strange problem. The problen is that i
> > am doing the total energy claculation of an elemental solid in the two
> > crystal structure.
> > (a)Crys type     rmt       rmt*kmax            lowest  energy
> > AlB2-type      2.0       10.0                for  this energy is lowest
> > Orthorhombic    2.0       10.0
> >
> > (b)
> > AlB2-type        1.8       9.0
> > Orthorhombic     1.8       9.0                 for this energy loewst
> >
> > In all these calcultaion I used the GGA-ex-correlation.
> >
> > So my question is that why calculation with two different RMT values
> > stablizes two diffrent structure.The culations are being done at the same
> > volume compression.
> >
> > I will be very thakfull for any suggestion
> >
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> >
>
> --
> Steven Homolya
> School of Physics and Materials Engineering
> Monash University, VIC 3800
> Australia
> Tel: +61 3 9905 3694
> Fax: +61 3 9905 3637
>
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