[Wien] Fixed spin moment calculations

Peram sreenivasa reddy Sat, 29 Mar 2014 05:18:07 -0700

Dear WIEN2k,

                    I am working on magnetic compound. For my system i got
total magnetic moment 1.95 bohr magneton. Now i want to do fixed spin
moment calculations.

          My quires are
1). To do fixed spin moment calculations, first i have to initiate the
calculations in spin polarized case after that i have to give the run
command like "runfsm_lapw -m 1.95 -ec 0.000001".
Is it correct way or give any suggestions?

2). To check weather this magnetic moment is correct or not i have to take
different magnetic moment values like 0.5, 1.0, 1.5, 2.0, 2.5, 3.0. For all
the values i have to run scf and check the total energy for each fsm value.
After this i have to plot total energy verses magnetic moment values. In
this plot where i get the minimum energy for a particular fsm value, that
magnetic moment value i should have to consider.
Is this correct procedure?

Please suggest me further.

Thank you very much in advance.

_________________________________

Re: [Wien] Fixed spin moment calculations

tran Sat, 29 Mar 2014 05:26:20 -0700

Yes, this is the correct procedure.

Re: [Wien] Reg: Fixed spin moment calculations

Peter Blaha Sun, 30 Mar 2014 22:51:12 -0700


Step 2) is the correct thing, but at least you should also add a total energy for M=0. And if the normal runsp calculation gives you the lowest total energy compared to all your fsm calculations, this is the proper solution.
However:   do you know   WHY   you want to make a fsm calculation ?
The  FSM method is used in 2 cases:

a) The total energy of more than ONE magnetic/non-magnetic calculations is almost identical. You may see this in a normal scf calculation that it converges very slowly (or not at all) or the calculations of runsp_c and runsp (zero and finite moments) give almost the same energy. b) You obtained some solution with runsp, but you want to search for another (eg. a high-spin or low-spin) solution. In this case you have to estimate what would be the total moment of such an solution and search the corresponding M-range.




Reference: https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10426.html