[Pw_forum] Fixed spin moment method & Phonon calculation

Subhradip Ghosh subhra at iitg.ernet.in
Wed Mar 18 10:24:32 CET 2009

I am interested in calculating phonn dispersions in a metallic system by
g the magnetization. To do that, I had fixed the magnetization to a
particular value and tried the phonon calculation. However, it failed
apprently because "the constrained magnetization is not implemented in the
phonon code". Therefore, my question is:
  Is phonon calculation not possible by fixing total magnetization with
the present QE code?

I had searched the archive to find answers but no definite solution was
found apart from a comment from Paolo which suggests that

"If the magnetization you choose is the ground state one, the two Fermi
energies would be the same. In that case, commenting out the check in
phq_readin.f90 should work. If you constrain the magnetization to a value
that is not the ground state, I have no idea what numbers will come out".

Does this mean that a phonon calculation(by commenting out the check in
phq_readin) by fixing the magnetization at a value other than the ground
state value is not reliable? The answer to this question is important to
me because I am interested in doing phonons by fixing total magnetization
at values other than the ground state value.

Help in this regard would be useful.


              Dr. Subhradip Ghosh
              Assistant Professor
              Department of Physics
            Indian Institute of Technology
               E-mail:subhra at iitg.ernet.in
               Phone: +91 361 2582717(O)
                      +91 361 2584717(R)
                Fax:  +91 361 2582749 (Physics)
                      +91 361 2690762 (General)

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