[Pw_forum] DFT+U and non-collinear calculations

[Pietro Bonfa']

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