[Wien] total energy when using -orbc for constant V-matrix

[wu@ph2.uni-koeln.de]

Dear Jose Mestnik Filho,

  Thanks for your email.

  Yes, for a well converged -orb case, its total energy can be
exactly restored in a continued -orbc calculation, only if the
missing Eorb term is added onto the 'total' energy calculated
using the -orbc.

  However, for some cases, e.g., a 'likely' low-spin S=1/2 Co2+
(normally Co2+ is high-spin 3/2), I need to use -orbc to 'stabilize'
this unusual low-spin Co2+ state. After I got a well converged
-orbc solution, I followed Peter Blaha's suggestion to continue
doing a normal -orb calculation (fix the Vorb without mixing in *inorb).
I found that the total energy only for the 1st loop might be meaningful
(the state is close to what I wanted it to be). Since the 2nd loop
onwards, dmat changed so much (the low-spin Co2+ is very unstable)
that the state is not any more the low-spin state. Therefore, the
previous comments of Laurence Marks and Stefaan Cottenier about using
-orbc to study some special orbital states should be of concern.

best regards -- H. Wu

> Dear Hua Wu,
> I remember that some time ago I had the same problem. I do not remember
> the version I used. At that time I noticed that summing up the
> results  :ENE + :EORB for the -orbc case gave the same result as :ENE
> of the -orb case.
> Look if it is your case also, and let us know the result.
> Regards,
> Jose.
>
>
>
>
> Em Sex, 2009-05-15 Ã s 15:32 +0200, Hua Wu escreveu:
>
>> Dear Peter Blaha, Pavel Novak, and Wien2k Users,
>>
>>   I tried to use LDA+U with -orbc flag to stabilize various orbital
>>   polarized
>> states in my calculations for some transition-metal oxides. In order
>> to  compare their total energies, I made a simple test, namely, run
>> 'LDA+U  with -orbc' for a well converged 'LDA+U with -orb' case. The
>> total energies are expected to be the same. However,  it is surprising
>> that in my current  calculations using the latest version, the total
>> energies change by several  Rydbergs. I am wondering if any term is
>> missing in the calculations of the total energy when using -orbc. In
>> addition, can one use -orbc to do structural relaxation like doing
>> LDA+U with -orb ?
>>
>> many thanks and best wishes -- H. Wu
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