[Pw_forum] DFT+U and non-collinear calculations

[Pietro Bonfa']

Dear Dr. Alexander Smogunov,

the short digression on the non-linear core corrections was intended to
explain why I need DFT+U to correctly reproduce the insulating and
magnetic ground state of La2CuO4.

I attached a modified version of example 11 (that I called example12).
I set all the parameters to zero just to check if everything is working
properly. I tried also with realistic values for U and J but I obtained
the same errors.

Thanks,
kind regards,
Pietro Bonfa'



On 04/29/2014 04:13 PM, Alex Smogunov wrote:
> Dear Pietro.
> It should work, in principle, at least for US PPs ... even though
> I do not understand what is the relation between  non-linear core
> corrections and
> the need for DFT+U together with spin-orbit, moreover you set up all the
> parameters
> essentially to zero. Anyway the code should run even in this case. Could
> you provide the complete
> input file, please?
> regards,
> Alexander
> 
> 
> 
> 2014-04-28 10:52 GMT+02:00 Pietro Bonfa' <pietro.bonfa at fis.unipr.it
> <mailto:pietro.bonfa at fis.unipr.it>>:
> 
>     Dear All,
> 
>     I would like to compare the total energies of various non-collinear
>     magnetic configurations in La2CuO4 (LCO).
> 
>     I started working with pseudopotentials from the PSLibrary, the GBRV
>     library and some home brewed norm conserving Cu pseudos. After a short
>     analysis I realized that the experimentally observed insulating and
>     antiferromagnetic ground state is obtained only if I remove non-linear
>     core corrections. This holds true for both my NC pseudos and the Cu
>     pseudo from PSL 1.0.0 (I didn't try GBRV).
> 
>     Nonetheless, since studying the magnetic ground state of LCO without
>     using non-linear core corrections does not make much sense to me, I
>     tried DFT+U with noncolin and lspinorb flags set to true.
> 
>     More precisely, I added the following lines to example 11 in the
>     QE-5.1rc1 release
> 
>         lda_plus_u=.true.
>         lda_plus_u_kind=1
>         Hubbard_U(1)=1.d-10
>         Hubbard_J(1,1)=1.d-10
>         Hubbard_J(2,1)=0.0
> 
>     Depending on the pseudopotential type (PAW, US or NC) I get errors like:
> 
>          from cdiaghg : error #        19
>          eigenvectors failed to converge
>     or
>          from cdiaghg : error #       109
>          S matrix not positive definite
> 
>     So my question is: is lda+u and non-collinear magnetism still not
>     implemented, is this a bug or me doing something utterly wrong?
> 
>     Thanks,
>     kind regards,
>     Pietro Bonfa'
> 
>     --
>     Pietro Bonfa' - PhD student
>     Dipartimento di Fisica e Scienze della Terra "Macedonio Melloni"
>     Viale delle Scienze 7A
>     43124 Parma - Italy
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> 
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-- 
Pietro Bonfa' - PhD student
Dipartimento di Fisica e Scienze della Terra "Macedonio Melloni"
Viale delle Scienze 7A
43124 Parma - Italy
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