Dear Sunetra InitSpin just sets up the initial density matrix to start the self-consistency cycle. The spin polarisation at the end of the SCF will be whatever spin-polarised DFT predicts including the sin polarisation on atoms that you did not include in the InitSpin block.
The initialisation is needed because - the non-polarised solution is still a solution (saddle point but a minimum until you break the spin symmetry), if both spin up and spin down densities were equal at the start they would remain equal till the end. (Siesta defaults to a vanilla ferromagnetic initialisation when spin polarised is true, just to allow the calculation to escape the spin-symmetric solution). - If the solution (minimum) is spin-polarised, there is always more than one (e.g. if there is a ferromagnetic solution, there will be always at least two, total spin being up or down). There can also be different minima as ferromagnetic and antiferro, etc. As in any minimisation with local minima, you’ll find one or the other depending where you start from. What matters at the end is the actual minima (solutions), especially the one (ones) with lowest energy. But you have to ind them and for that you have to try different starting points. Emilio > On Sep 24, 2018, at 7:44 AM, Sunetra Das <[email protected]> wrote: > > Dear siesta experts, > > Please help me clarify a confusion, as I am unable to clear my doubt from the > manual. I am using siesta 4.0 version. > > I want to study the effect of doping on a non-magnetic system. I have carried > out spin polazied calculation on the pristine system and the resulting total > magnetic moment was zero. I did the same with a single dopant atom with non > zero total magnetic moment. Now after I introduce two dopant atoms, I want to > see if the atoms are ferromagnetically coupled or antiferromagnetically, in > ground state. I use the data block DM.InitSpin to define the spin directions > of the two dopant atoms only. I have also turned the spin polarization option > to .true.. Do I need to specify the spin directions of the atoms of the doped > system in the DM.InitSpin data block or turning the spin polarization to > .true. takes care of the atomic spins outside the datablock? > > I want to see how the local magnetic moment of the atoms in the doped system > changes with introduction of dopant atoms. > > I have assumed the spins to be collinear. > > Thank you. > Regards, > Sunetra Das.
