Hi, Haibo Thank you for your reply. As Natalia said, more k-points just take more time. I tried to calculated only with the gamma point, and the results seem to be the same with those with the 5*5*5 Kpoints. I tried to fix the spin to zero, however, the results keep no change. I changed several parameters, like xc.functional, xc.authors, and even the pesudopotential. I found that xc.functional, xc.authors must keep LDA and PZ to promise reasonable results (0.79229 and -4.876558 for the bond length and bond energy), while the pesudopotentials (LDA or GGA) bring little influence to the result. I am really interested with your result PBE (siesta): 4.76 eV. Would you please send me the input files? I want to check what is wrong in my input files.
Thank you very much! Yours sincerely leila -----邮件原件----- 发件人: Haibo Guo [mailto:[email protected]] 发送时间: 2011年3月1日 0:18 收件人: [email protected] 主题: Re: [SIESTA-L] H2 binding Energy Only gamma point is needed for isolated molecules or atoms. Spin polarization can be included; you need a initial antiferromagnetic configuration for H2. But without spin, the results should be close because H2 molecules don't have net spin polarization. H2 should behave well with most functionals. Here are some of my results of the binding energy (eV per bond): PBE (siesta): 4.76 PBE (vasp): 4.54 HSE06 (vasp): 4.53 Hope this helps. Haibo 2011/2/28 Süle Péter <[email protected]>: > > Dear Leila, > > for me using siesta-2.0.2 with your fdf file (GGA/PBE, 5X5) > > 0.75 -31.5205 eV/H2 > 10. -25.4867 > inf -24.3496 > > Ec= ~ -3.5854 eV/atom (e.g. -7.17 eV bond energy) > > which is not bad. I mean one can not necessariliy expect with GGA a > better value. Hybdrid functionals should give better results. The > issue of better VASP values should be discussed in a more detail by > experts since indeed quite oftenly happens. > > Best regards, Péter Sule > > > ---------------------------------------------------- > Dr. Peter Sule > senior research associate > Institue for Technical Physics and Materials Science (MTA-MFA), > Konkoly-Thege M. 29-33, Budapest, Hungary > tel.: (36) 1 392 2222/3605 > fax.: (36) 1 392 22 73 > www.mfa.kfki.hu/~sule / [email protected] > ----------------------------------------------------- > > > On Mon, 28 Feb 2011, leila wrote: > >> >> Hi, everyone, >> >> >> >> I want to do some calculations on the H effect in Fe, before which I >> have to promise the accuracy of H potential. I first make a simple >> tests of the H2 properties, including the H-H distance in H2, and >> also the binding energy (Defined as the energy difference of the H2 >> molecular and two isolated H atom). >> >> I find the H-H distance is around 0.75 Ang, which is near to the >> experimental value of 0.741 Ang, for both LDA and GGA pseudopotential. >> However, the binding energy is always not correct, calculated to be >> around >> -7.2 eV (The experimental and VASP results are all around -4.55 eV). >> My input file for H are in the attachments. >> >> I don’t know where the issues are. Could anybody help me? >> >> >> >> In addition, I find that the spin polarization contributes a lot in >> the >> H2 >> calculations. When I add the spin polarization effect in the VASP and >> SIESTA calculations, the H-H distance becomes to 2.89 Ang, and the >> binding energy is approaching to 0 eV. Can anyone explain this to me. >> Because Fe is magnetic materials, I have to consider spin >> polarization effect in my calculation. >> >> >> >> Thank you in advance! >> >> Yours sincerely, >> >> Leila >> >> >> >> >
