Hi, Weijia, In fact, you can have a look at mix_rho.f90 for detailed agorithms used in QE package for density mixing scheme . The scheme is just modified Broyden's method for charge density mixing , please see D.D. Johnson PRB 38, 12807 (1988).
regards, On Sun, Mar 1, 2009 at 8:09 PM, vega lew <quantumdft at gmail.com> wrote: > Dear friend, > > I found there is few supporting materials decribing what the exact meaning > for mixing_beta. do you think the following paragraph from the manual of > Materials Studio is suitable for this parameters? > > ------------------------------------------------ > > Electronic minimizer: Specify the electronic minimization method to be > used for the SCF calculation. Two options are available, Density Mixingand All > Bands/EDFT. > > Tip. The Density Mixing option is recommended, particularly for variable > occupancy calculations. The All Bands/EDFT method is usually slower and > requires more memory. However, the EDFT scheme is recommended for metallic > systems where converging electronic structure using Density Mixing option > proves problematic. > > Charge: Specify the amplitude for charge density mixing (i.e., the > amplitude of the output charge density to mix with the input charge density > to obtain input for the next iteration). > > Note. This option is enabled only if the Density Mixing minimization > method is selected. > > Spin: Specify the amplitude for spin density mixing, i.e. the amplitude of > the output spin density to mix with the input spin density to obtain input > for the next iteration. > > Note. This option in enabled only for spin-polarized calculations using > the Density Mixing minimization method. > > ------------------------------------------------- > > Shoul I consider the mixing_mode option in PWSCF is equal to Density > Mixing option in MS, and value of mixing_bate in PWSCF is equal to the one > of Charge in MS? > > Do you think I should swich on the boardening by 'occupations', 'degauss' > and 'smearing' command in PWSCF? > > I also found no detail description for this three options. > > do you think the following text suitable for the three command in PWSCF? > > ----------------------------- > > Smearing: Specify the broadening to be applied to the electronic > occupation. > > Note. This option is enabled only for variable occupancy calculations. > > ----------------------------- > > If the answer is no, could you please give me some suggestion to > understanding the command and make a better use of it. > > thank you so much for reading > > > best wishes, > > vega > > > > On Sun, Mar 1, 2009 at 7:44 PM, vega lew <quantumdft at gmail.com> wrote: > >> Dear APSI >> >> thank you for you suggestions to me. >> >> I will try it ASAP. >> >> vega >> >> On Sun, Mar 1, 2009 at 5:08 PM, Ari Paavo Seitsonen < >> ari.p.seitsonen at iki.fi> wrote: >> >>> >>> Dear Vega, >>> >>> Just my guesses and suggestions: One could try mixing of the density, >>> like >>> >>> &electrons >>> mixing_beta = 0.7 >>> / >>> >>> (or a value even smaller than 0.7, or some other parametres for the >>> mixing) since with a defect you might now have defect levels in the band >>> gap, leading to a more difficult a convergence. Eventually one could also >>> switch on the broadening of the occupation numbers, eventually switching it >>> off for the physical/production jobs, but just to check if the problem in >>> convergence comes due to this. >>> >>> And in the original paper the authors discuss spin-polarisation, one >>> might test also this (nspin = 2), with different initial magnetisations >>> [starting_magnetization(xx) = ...] for the atoms surrounding the defect. >>> >>> Greetings, >>> >>> apsi >>> >>> >>> On Sun, 1 Mar 2009, vega lew wrote: >>> >>> Dear all, >>>> >>>> I am planning to calculate the Oxygen vacancy properties of TiO2 >>>> surfaces. >>>> The calculation for the ideal surfaces are quite normal and the results >>>> are >>>> in line with the one that literature reported. But, when I tried to >>>> calculate the anatase 101 surface with an Oxygen vacancy (O2c was >>>> removed >>>> directly from the stoichiometric Anatase 101as described in J. Phys. >>>> Chem. C >>>> 2007, 111, 16397-16404, I encounter the problem of convergence for SCF >>>> cycle. I tried to add 20% more empty band to the system the problem >>>> still >>>> laid in. How could I overcome the problem? >>>> >>>> my input file was attached at the bottom of the mail >>>> >>>> thank you for reading. Any hints will be appreciated. >>>> >>>> vega >>>> >>>> >>> ... >>> >>> >>> >>>> &SYSTEM >>>> ibrav = 8, >>>> celldm(1) =19.3269, >>>> celldm(2) = 1.1094, >>>> celldm(3) = 1.7450, >>>> nat = 71, >>>> ntyp = 2, >>>> nosym = .true., >>>> ecutwfc = 30, >>>> ecutrho = 300, >>>> / >>>> >>>> &ELECTRONS >>>> >>>> / >>>> >>>> &IONS >>>> ion_dynamics = 'bfgs', >>>> / >>>> >>>> >>> -- >>> >>> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- >>> Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / >>> http://www.iki.fi/~apsi/<http://www.iki.fi/%7Eapsi/> >>> IMPMC, CNRS & Universit? Pierre et Marie Curie >>> Tel: +33-1-4427 7542, Fax: +33-1-4427 3785, GSM: +33-6-6736 3820 >>> _______________________________________________ >>> Pw_forum mailing list >>> Pw_forum at pwscf.org >>> http://www.democritos.it/mailman/listinfo/pw_forum >>> >>> >> >> >> -- >> >> ================================================================================== >> Vega Lew ( weijia liu) >> PH.D Candidate in Chemical Engineering >> State Key Laboratory of Materials-oriented Chemical Engineering >> College of Chemistry and Chemical Engineering >> Nanjing University of Technology, 210009, Nanjing, Jiangsu, China >> >> ****************************************************************************************************************** >> Email: vegalew at gmail.com >> Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, >> Nanjing, Jiangsu, China >> ****************************************************************************************************************** >> >> > > > > -- > > ================================================================================== > Vega Lew ( weijia liu) > PH.D Candidate in Chemical Engineering > State Key Laboratory of Materials-oriented Chemical Engineering > College of Chemistry and Chemical Engineering > Nanjing University of Technology, 210009, Nanjing, Jiangsu, China > > ****************************************************************************************************************** > Email: vegalew at gmail.com > Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, > Nanjing, Jiangsu, China > ****************************************************************************************************************** > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- Hai-Ping Lan Department of Electronics , Peking University , Bejing, 100871 lanhaiping at gmail.com, hplan at pku.edu.cn -------------- next part -------------- An HTML attachment was scrubbed... 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