udayagiri sai babu wrote: > Dear prasenajit > thank you for your valuable inputs > > On Fri, Sep 11, 2009 at 2:43 PM, Prasenjit Ghosh > <prasenjit.jnc at gmail.com <mailto:prasenjit.jnc at gmail.com>> wrote: > > For Ti atom, the electronic configuration is [*Ar*].*3d*^2 .*4s*^2 > . So the magnetization should be 2.0 Bohr magneton due to the two > electrons in the d-orbital, which is not what you are getting from > your calculation. > > Also your smearing contribution is -0.00972779 Ry (about 0.1 eV), > which I would say very high. If you would have find the correct > magnetic ground state, then this should have been 0.0 Ry. > > As far as the bulk system is concerned, I'm not sure. It depends how > Ti bulk behaves. You can search in the literature to find out what > values of degauss other people have used.
If you want to obtain the correct ground state and magnetization for the isolated Ti atom, I suggest you to use either occupations=fixed and tot_magnetization=2 (but this calculation will not converge, probably), or better to use occupations='from_input' and use the OCCUPATIONS card to specify the correct electronic configuration. Another solution could be to use smearing and the constrained-magnetization method, though I never used it for isolated atoms. HTH GS > > Mixing beta doesn't effect the energy of the system. It just helps > you in convergence. > > > Prasenjit. > > 2009/9/11 udayagiri sai babu <udayagiri3 at gmail.com > <mailto:udayagiri3 at gmail.com>> > > Dear prasenajit this is the part of my output for the posted > input file. (smearing contribution is there! though it is small > ) is the degauss value too high for isolated atom or it is high > for bulk calculation also? because i use around 0.01 Ry value > for all my calculations. Does the mixing beta value effect the > energy of the system? > > one-electron contribution = -155.91791626 Ry > hartree contribution = 74.49216944 Ry > xc contribution = -14.37611953 Ry > ewald contribution = -20.42854186 Ry > smearing contrib. (-TS) = -0.00972779 Ry > > total magnetization = 3.24 Bohr mag/cell > absolute magnetization = 3.24 Bohr mag/cell > > convergence has been achieved in 34 iterations > > > On Fri, Sep 11, 2009 at 2:06 PM, Prasenjit Ghosh > <prasenjit.jnc at gmail.com <mailto:prasenjit.jnc at gmail.com>> > wrote: > > Dear Udayagiri, > > First of all it's not clear whether you have any question > other than whether your input file is correct. > > Now some comments about your input file: > > (a) while doing calculations for any zero dimensions you > should always set nosym =.true. > (b) Your value of degauss is too high.....you should use > some value around 0.001 Ry. According to my experience, > doing cal. for a single atom is tricky, specially when you > are using a smearing. Even that doesn't confirm you will get > the correct ground state for the atom. So what you should do > is at the end of the calculation check the values of the > total magnetization, absolute magnetization and the smearing > contribution. The last term should be exactly zero. > (c) You don't need to set tstress and tprnfor true. > (c) mixing_beta= 0.7 too large.....I would put something > smaller....0.3 > (d) I hope you have checked the convergence of ecut rho & > ecutwfc. > > Prasenjit. > > 2009/9/11 udayagiri sai babu <udayagiri3 at gmail.com > <mailto:udayagiri3 at gmail.com>> > > Hi everybody > I want to calculate the cohesive energy of Titanium for > that i need to calculate the energy of an isolated atom > previously in the forum somebody has suggested me to do > spin polarisation calculation for the isolated atom. I > have written an input file accordingly some one can see > and tell me if my input script is true. I have read the > forum archives on this topic but they are not exactly > answering my question. Can somebody please help me. > * > Input file for isolated atom * > > &control > calculation = 'scf', > restart_mode='from_scratch', > outdir='/home/sai/temp', > prefix='titanium' > pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/', > tstress = .TRUE., > tprnfor = .TRUE., > / > &system > ibrav=1 > celldm(1)=20, > nat=1, > ntyp=1 > ecutwfc=25, > ecutrho=250, > occupations='smearing', > smearing='mv', > degauss=0.010000 > nspin=2 > starting_magnetization(1)=0.2 > / > &electrons > conv_thr=1.D-8, > diagonalization='david', > mixing_mode='plain', > mixing_beta= 0.7, > / > ATOMIC_SPECIES > Ti 47.867 Ti.pbe-sp-van_ak.UPF > ATOMIC_POSITIONS (crystal) > Ti 0.00000000 0.00000000 0.00000000 > K_POINTS GAMMA > -- o ------------------------------------------------ o | Gabriele Sclauzero, PhD Student | | c/o: SISSA & CNR-INFM Democritos, | | via Beirut 2-4, 34014 Trieste (Italy) | | email: sclauzer at sissa.it | | phone: +39 040 3787 511 | | skype: gurlonotturno | o ------------------------------------------------ o