Dear Emilio sir , Thank you very much for your help.
On 25 September 2018 at 14:06, Emilio Artacho <ea...@cam.ac.uk> wrote: > 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 <sunetra.das...@gmail.com> > 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. > >
