Dear users, dear Kay,
I have a probably naive question: I am calculating the band structure of a cuprate system that should not be magnetic in GGA, but is AFM adding some U value. In GGA, I set some initial local B fields (everything collinear) on two different Cu atoms (let's call them Cu1 and Cu2). Let's say +2 on Cu1 and -2 on Cu2. I set reducebf = 1. (so no action on the B field in each scf step, right?). I obtain a converged solution to a finite magnetic moment locally on the two Cu atoms (actually with a reversed sign, i.e. - 0.13 on Cu1 and +0.13 on Cu2).
The point is that when I set reducebf = 0.5 , the system converges to a non-magnetic solution (zero local moments on Cu1 and Cu2), with clearly strong modification of the band structure close to Fermi, which is exactly what I want to check with an all electron calculation.
So I have a reducebf-dependent solution. Am I doing something wrong? The total energies differ on the third decimal.
Is there any "proper" choice of reducebf parameter to resolve this ambiguity?
The stating b-field should be quite large if you want to keep reducebf to 0.5. Can you send me the input file and can test it.
You get what one expects.
The effect of reducebf is that the initial b-field is reduced with the given factor in each iteration. When reducebf<1 the magnetic field is vanishingly small at convergence. However, with reducebf=1 you keep the given applied field throughout. Hence you should expect different solutions for the two cases, reducebf <1 or =1, as you also see. From the small Cu moment it consistent with that it is only induced by the applied field in the reducebf=1 case.
Exactly what Lars said. But if the starting bfield (bfeildmt or bfieldc) are small, the difference in moment in two calculations cannot be this large. I would say increase the starting bfield by an order in magnitude (something like 0 0 1.5 ) and then take reducebf to 0.5 and you should get the same answer as for the case of reducebf 1.
Dear Sangeeta and Lars, thank you for your answers, that clarified my problem
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