Dear Both- A little bit confused. So Salvador you are saying I can run two tests. one w/o totalspin and fix spin one w/. If the one w/ totalspin 0.0 and fixspin true give lower total energy, I can move on to phonon calculation? Thanks
Best Regards ------- Zhen (Alex) Huang Ph.D. Student Nanoscale Transport Research Group Laboratory for Computational Methods in Emerging Technologies Cooling Technologies Research Center School of Mechanical Engineering Purdue University Tel: 765 237 9733 On Wed, Mar 3, 2010 at 10:17 AM, Barraza-lopez, Salvador < [email protected]> wrote: > > Dear Zheng and Marcos, > To check Marcos' point one could add the following lines to the input > file: > > totalspin 0.0 > fixspin True > > If the total energy with with these added lines is bigger (in absolute > value) than the one you have just obtained, then you are fine, and just need > to use this constraint all the time. > > Best regards, > -Salvador. > > ----- Original Message ----- > From: "Marcos Veríssimo Alves" <[email protected]> > To: [email protected] > Sent: Wednesday, March 3, 2010 9:43:32 AM GMT -05:00 US/Canada Eastern > Subject: Re: [SIESTA-L] Fwd: Titanium Phonon Calculation Re: Titanium > calculation help posted earlier > > Salvador and Zhen, > > Forgive me if I'm wrong, but couldn't magnetic states be displayed in > DFT calculations even if the material is not magnetic in its ground > states? This could simply be a metastable ground state, and in this > case what one should really compare is the total energy of the system > in both states, magnetic and paramagnetic. What would really worry me > is if, metallic Ti being paramagnetic, the magnetic state were lower > in energy. > > And, on a personal note, I'd trust more the Abinit pseudo than the one > generated in a plug-and-play fashion by the Octopus website - there is > always a tendency to use the rc's supplied by default in the > interface, which are not necessarily good ones. Moreover, the Octopus > website interface to the pseudopotential generator allows for less > flexibility than a mastery of the ATOM program file format. Abinit > pseudos are often tried and tested, even though it is imperative to > test every pseudo in simple cases before going for the real thing. > Just my 10 cents on the subject. > > Cheers, > > Marcos > > On Wed, Mar 3, 2010 at 3:21 PM, Barraza-lopez, Salvador > <[email protected]> wrote: > > > > Dear Zhen, > > I would recommend that you change the cuttof radii in your pseudo and > > regenerate it (perhaps 2.0 radii for all your channels, but you can play > > with it). Then test it again for polarization in the bulk. > > If you never get spin polarization to be zero, try turning on > relativistic > > corrections, and even core corrections. Just be methodic and go for each > of > > these things (radii, relativistic corrections, core corrections) > > sequentially. The atom manual should be sufficient to guide you in the > > process. The process should be: Generate your pseudo with atom, run a > SIESTA > > calculation with that one and record the magnetization with a standard > basis > > set, if polarization is not zero, go back and generate a new pseudo, and > > iterate as needed. > > > > Whenever your polarization is zero, you'll discover that the lattice > > constant in the bulk should be reasonable; then you can proceed to study > > phonon dispersions. > > > > Best regards, > > -Salvador. > > > > > > > > ----- Original Message ----- > > From: "Zhen Huang" <[email protected]> > > To: [email protected] > > Sent: Tuesday, March 2, 2010 8:20:42 PM GMT -05:00 US/Canada Eastern > > Subject: Re: [SIESTA-L] Fwd: Titanium Phonon Calculation Re: Titanium > > calculation help posted earlier > > > > Dear Salvador- > > I turned on the spin-polarized. I find the Qup-Qdown is not zero. > > siesta: Total spin polarization (Qup-Qdown) = 4.856526. I am using GGA > > PBE generated from http://www.tddft.org/programs/octopus/pseudo.php > Lodger > > radii 3. I also tried the GGA psf converted from ABINIT which I download > > from SIESTA website the Qup-Qdown is about 4.939. Can you let me know how > > can I fix this? Thanks. > > Best Regards > > ------- > > Zhen (Alex) Huang > > Ph.D. Student > > Nanoscale Transport Research Group > > Laboratory for Computational Methods in Emerging Technologies > > Cooling Technologies Research Center > > School of Mechanical Engineering > > Purdue University > > Tel: 765 237 9733 > > > > > > On Mon, Mar 1, 2010 at 10:14 AM, Barraza-lopez, Salvador > > <[email protected]> wrote: > >> > >> Hi all, > >> > >> > >> > >> I've been following this post and want to mention something else that > has > >> not come out yet. Ti has in the valence two d and two s electrons. > >> d-electrons are responsible for magnetic behavior. So, I'd like to ask: > Have > >> you taken your Ti pseudo (is it LDA, GGA pseudo?) and ran a > >> spin-polarized(!) bulk calculation on the HCP phase (two atoms in unit > cell) > >> ? Don't worry about the basis now, just use the standard one. > >> > >> > >> > >> If you've done this, is your total spin up minus spin down is equal to > >> zero? > >> > >> Titanium should be non-magnetic. If you get a large spin polarization > >> here, there is no point in keep going further. > >> > >> If you are sure your bulk Ti run is non-magnetic, please disregard my > >> post. > >> > >> > >> > >> Best regards, > >> > >> -Salvador. > >> > >> ----- Original Message ----- > >> From: "Zhen Huang" <[email protected]> > >> To: "SiestaMailingList" <[email protected]> > >> Sent: Monday, March 1, 2010 8:19:00 AM GMT -05:00 US/Canada Eastern > >> Subject: [SIESTA-L] Fwd: Titanium Phonon Calculation Re: Titanium > >> calculation help posted earlier > >> > >> Dear Friends- > >> I had trouble of reply my old post. This is a following question about > >> Titanium. After I increased the kgrid_cutoff to 25 Ang. The results do > >> become better. However, when I am running 3*3*3 supercell calculation > the > >> dispersion curve becomes like attached. I am running a 5×5*5 case (on 4 > >> processors) now however, the calculation becomes really slow. I wonder > what > >> is the best way to run it faster. Again my input files are attached. > Please > >> give me some advice. Further, shall I comment kgrid_cutoff in > vibrational > >> properties calculation? I tried it but it gives me totally wrong > results. I > >> wonder if I can speed up the calculation by doing anything. I deeply > >> appreciate your help. > >> > >> Best Regards > >> ------- > >> Zhen (Alex) Huang > >> Ph.D. Student > >> Nanoscale Transport Research Group > >> Laboratory for Computational Methods in Emerging Technologies > >> Cooling Technologies Research Center > >> School of Mechanical Engineering > >> Purdue University > >> Tel: 765 237 9733 > >> > >> > >> > >> -- > >> Salvador Barraza-Lopez > >> Postdoctoral Fellow > >> School of Physics > >> The Georgia Institute of Technology > >> > >> Office N205 > >> 837 State Street Atlanta, Georgia 30332-0430 U.S.A > >> Tel: (404) 894-0892 Fax: (404) 894-9958 >
