[Pw_forum] About Pseudo-Potential generation
Dear Paolo, Thanks very much for your answering. But I still do not fully understand your answers about fractional occupation. In my example, some may use [Ne]3s1.5 for Mg. And you said that this is for computational convenience. Can you elaborate more on this point? By the way, if this config is used, should I correspondingly set zval=1.5 , instead of let it default? Thanks a lot! Lawrence ___ YM - ??? http://messenger.yahoo.com.hk -- next part -- An HTML attachment was scrubbed... URL: /pipermail/attachments/20070125/87cda318/attachment.htm
[Pw_forum] Debye temp, phonon DOS and sum rules.
On Jan 25, 2007, at 17:59 , Miguel Mart?nez Canales wrote: > On a side note, the difference between a 40 40 40 and a 12 12 12 > phonon > dos is like night and day. Is such difference to be expected? maybe not like "day and night", but it takes quite a dense grid if you want to see a DOS with all the singularities as in textbooks > I suppose it's related to the way the phonon dos is computed within > the code. it is a rather straightforward tetrahedron method > Finally, it might interest you to know that fitting a parabola to > the low w > regime and using the pseudopotential's equilibrium lattice parametre, > the Debye temperature is 152 K, very close to the value presented in > Table 23.3 of Ashcroft's and Mermin's book. so now we know that Ashcroft's and Mermin's book is correct :-) Paolo --- Paolo Giannozzi, Democritos and University of Udine, Italy
[Pw_forum] Debye temp, phonon DOS and sum rules.
Dear Paolo, Thank you very much for your answers. I am particularly thankful for the reference to Nicola Marzari's paper. MMC> 3) Is the hoop I'm seeing at around 17cm-1 a van Hove singularity I MMC> haven't covered in my dispersion curves or something more profound? PG> hard to say, especially without seeing OK, as I've seen attachments sometimes fail, I'll later provide the first 21 files of my phdos. Anyway, I think I've found the issue. It was related to the nk's I was using to get the phonon density of states. It seems that a regular 6,6,6 or 8,8,8 mesh is not enough, although with that mesh the IFC seems to have converged. Using a 20,20,20 or higher mesh would yield a more logical behaviour. $ head -21 na.phdos -0.2601E-05 0.E+00 0.1000E+01 0.4175E-05 0.2000E+01 0.1670E-04 0.3000E+01 0.3758E-04 0.4000E+01 0.6680E-04 0.5000E+01 0.1044E-03 0.6000E+01 0.1503E-03 0.7000E+01 0.2046E-03 0.8000E+01 0.2672E-03 0.9000E+01 0.3382E-03 0.1000E+02 0.4175E-03 0.1100E+02 0.5052E-03 0.1200E+02 0.6012E-03 0.1300E+02 0.7056E-03 0.1400E+02 0.8183E-03 0.1500E+02 0.2017E-02 0.1600E+02 0.2252E-02 0.1700E+02 0.2474E-02 0.1800E+02 0.2683E-02 0.1900E+02 0.2880E-02 0.2000E+02 0.3064E-02 One can easily see the hop and the lack of parabolic behaviour above 14 cm^-1. On a side note, the difference between a 40 40 40 and a 12 12 12 phonon dos is like night and day. Is such difference to be expected? I suppose it's related to the way the phonon dos is computed within the code. Finally, it might interest you to know that fitting a parabola to the low w regime and using the pseudopotential's equilibrium lattice parametre, the Debye temperature is 152 K, very close to the value presented in Table 23.3 of Ashcroft's and Mermin's book. Thanks again, Miguel -- Miguel Mart?nez Canales Dto. F?sica de la Materia Condensada UPV/EHU Facultad de Ciencia y Tecnolog?a Apdo. 644 48080 Bilbao (Spain) Fax: +34 94 601 3500 Tlf: +34 94 601 5437 "If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas." George Bernard Shaw
[Pw_forum] Debye temp, phonon DOS and sum rules.
On Jan 24, 2007, at 9:50 , Miguel Mart?nez Canales wrote: > 1) Is trying to calculate the Debye temperature from the phonon DOS > too na?ve? It should be possible; for sufficiently isotropic dispersions you might also try to estimate the coefficient c in w(q)=cq for q->0 > 2) What are the practical differences between simple and crystal asr? 'simple' asr consists in modifying the diagonal term only of the force constant matrix so that the sum over all atoms of the induced forces is zero. 'crystal' asr modifies the matrix in such a way to conserve the symmetry, I think. > Could be translated to: What does "optimized corrections of the IFC" > in pwtools/q2r.f90 mean? it means that you have to read the original reference, if any (try this: PRB 71, 205214 (2005) ) > 3) Is the hoop I'm seeing at around 17cm-1 a van Hove singularity I > haven't > covered in my dispersion curves or something more profound? hard to say, especially without seeing Paolo --- Paolo Giannozzi, Democritos and University of Udine, Italy
[Pw_forum] Zr, Y and Lu NC pseudo
Dear all I am intensively trying to build (or convert) pseudo potentials of Zr, Y and Lu to make phonon calculations. Unfortunately, all the PP?s I got, gave weird band structures, very far from what I got with US PPS. As anybody these PPS files or a reliable way to check if a PP is ok or not before trying it in a very long calculation? Thanks for your help. J?r?mie Jeremie Teyssier DPMC 24 quai Ernest Ensermet CH-1211 Geneve 4 SUISSE tel: (41) 22 379 65 78 fax: (41) 22 379 68 69 web: <http://optics.unige.ch/jeremie/home_jeremie.html> http://optics.unige.ch/jeremie/home_jeremie.html -- next part -- An HTML attachment was scrubbed... URL: /pipermail/attachments/20070125/b50f4bc9/attachment.htm
[Pw_forum] nuclear charge change
On Thu, 25 Jan 2007, Amin Babazadeh wrote: AB> Dear users AB> Would you please tell me that how i can change nuclear charge in quantum AB> espresso code.We know that the nuclear charge in H(hydrogen) is 1 (Z=1) but AB> in my calculation it should be .5 (Z=.5) or 1.5 (Z=1.5) but i don't how AB> to do it in espresso. dear amin, you will have to create special pseudopotentials for that. this is not an entirely unusual case, so perhaps somebody here on the list has potentials for that case and can help you out. cheers, axel. AB> I will appreciate if helps me AB> sincerely yours AB> AB> -- === Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu http://www.cmm.upenn.edu Center for Molecular Modeling -- University of Pennsylvania Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323 tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425 === If you make something idiot-proof, the universe creates a better idiot.
