[Wien] Emax in case.in1 within spin-orbit coupling calculations

[Stefaan Cottenier]

Just as the total energy will decrease asymptotically (=forever) if you 
increase RKMax, it will decrease asymptotically if you increase Emax. 
How do you find the appropriate RKMax? ==> not by monitoring the total 
energy as such, but either energy *differences* or your observable 
property of interest. The same applies here: either you observe the 
energy difference (between e.g. two cases with a different magnetic 
order), or you monitor an observable property that depends on spin-orbit 
coupling (e.g. orbital contribution to the magnetic moment).

Stefaan



On 19/03/2012 11:26, hyunjung kim wrote:
> Dear all,
>
> I have some question on calculation including spin-orbit coupling (SOC).
>
> In according to the manual, the second-variational procedure requires to
> include many more unoccupied states to be calculated. And it can be
> controlled by increasing the energy maximum (Emax) which eigenvalues
> shall be searched.
>
> For the Emax which defines the number of eigenvalues to be calculated, I
> have used Emax=2.5 Ry in non-SOC and 5.0 Ry for SOC. Thus, the number of
> eigenvalues in SOC calculation were increased by about 2 times larger
> than that of non-SOC. And also I have check the convergence in the
> function of Emax value. For non-SOC calculations, it does not depend on
> Emax value as expected. However in the case of SOC calculations, total
> energy was depend on the Emax value. Larger Emax results the total
> energy go down. But up to 10Ry of Emax, I cannot find convergence in
> total energy. You can find the numbers below.
>
> system : Bismuth bulk (including SOC) ; total energy
> Emax = 2 ; E(total) = -86326.2333 Ry
> Emax = 2.5 ; E(total) = -86326.2420 Ry
> Emax = 3 ; E(total) = -86326.2454 Ry
> Emax = 4 ; E(total) = -86326.2527 Ry
> Emax = 5 ; E(total) = -86326.2577 Ry
> Emax = 7 ; E(total) = -86326.2634 Ry
> Emax = 10 ; E(total) = -86326.2662 Ry
>
>
> Questions are,
> 1. Why the unoccupied states affect the total energy in the case of SOC
> been included?
> 2. Is there appropriate suggestions taking Emax value?
> 3. Should the total energy converged as the function of Emax?
> 4. Within same Emax restriction (i.e. same parameters), could the total
> energy be compared between different geometries?
>
> Thank you.
> Best regards,
> Hyun-Jung Kim.
>
> ------------------------------------------------------------------------
> Hyun-Jung Kim (Ph.D student)| phone : ++82 10 7335 7889
> Department of Physics|
> Hanyang University| e-mail: angpangmokjang at h
> <mailto:hyunjung at fhi-berlin.mpg.de>anmail.net <http://anmail.net>
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