Some times I have the impression that, in this list, some users did not realize that people here are helping each other for free and in their free-time.
Indeed I´m not one of the "heroes" in this list - like Marcos Alves or Andrey Postnikov, who are always helpful - but still, it is quite annoying opening the mails to see if I can quickly help and figure out that someone is delivering orders to the other users, or expecting us t o make his job. That is simply not nice! Now back to the point! Testing pseudo potentials and basis are usually hard work! If the pseudos available in the repository does not match your necessities ... you have to generate one by your own. Concerning on the basis set : Usually, the DZP basis are enough for most things, but keep in mind that in some cases they are not and triple zeta may be necessary ( again, you have to test it ). If you are going to calculate big systems... optimizing the basis with some simplex algorithm will save you computation time in the and ... If we going to calculate small middle size systems, you can optimize the basis using the parameter PAO.EnergyShift. The final result may be not the most computationally efficient ... but accurate. Anyway : YOU have to test it! I also would advise you to take a look on the User's Guide ... I my case I work always with the manual opened! Regards Thu, Jan 20, 2011 at 1:22 PM, suman kalyan sahoo <[email protected]>wrote: > Sir, > I am sending the input file taken for the band structure calculation > for Sn in beta phase (BCT) as well as some literature data .I am also trying > with different pseudopotential and basis set for band structure calculation > but unable to represent the beta phase where as alpha (dimond phase ) > band structure reproduce easily. > Please check the input and suggest me what basis set and pseudo is suitable > for bulk Beta Sn (body centered tetragonal structure). > > Suman Kalyan Sahoo > > --- On *Wed, 19/1/11, Marcos Veríssimo Alves < > [email protected]>* wrote: > > > From: Marcos Veríssimo Alves <[email protected]> > Subject: Re: [SIESTA-L] Fw: mismatch in band structure of bulk tin in beta > phase. > To: [email protected] > Date: Wednesday, 19 January, 2011, 9:51 PM > > Suman, could you give us a more precise idea of how the band structure, > lattice parameters and cohesive energy compare with the data in the > literature (that is, providing numbers and an illustration of the band > structure)? > > With the very scarce information you provide I can only think of trivial > mistakes, such as not placing the correct coordinates of k-points in the BZ > of the beta Sn phase, or incorrect coordinates for this same phase. Check > for that. > > Marcos > > On Wed, Jan 19, 2011 at 3:38 PM, suman kalyan sahoo < > [email protected]> wrote: > > > > --- On *Wed, 19/1/11, suman kalyan sahoo <[email protected]>* wrote: > > > From: suman kalyan sahoo <[email protected]> > Subject: mismatch in band structure of bulk tin in beta and alpha phase. > To: [email protected] > Date: Wednesday, 19 January, 2011, 12:17 AM > > Dear users > > I am doing calculation on bulk beta-Sn (tin),as well as alpha tin. > I am taking the the > pseudo potential given in siesta home website > first few lines are > Sn pb nrl nc > ATM 3.2.2 9-APR-07 Troullier-Martins > 5s 2.00 r= 2.43/5p 2.00 r= 2.49/5d 0.00 r= 2.82/4f 0.00 r= 2.82/ > 4 0 1176 4.957504353333E-05 1.250000000000E-02 4.000000000000 > > > Radial grid follows > 6.235772827088E-07 1.254998202050E-06 1.894361418827E-06 > 2.541766834843E-06 > 3.197315608511E-06 3.861110170662E-06 4.533254240545E-06 > 5.213852842040E-06 > 5.903012320063E-06 6.600840357183E-06 7.307445990452E-06 > 8.022939628438E-06 > > > > and basis set for Sn as follows > %block PAO.Basis > Sn 2 > n= 5 0 2 > 6.030 4.773 > n= 5 1 2 P 1 > 7.675 > 5.615 > %endblock PAO.Basis > as well as > %block PAO.Basis > > # Define Basis set > > > Sn 3 # Species label, number of l-shells > n=5 0 2 P 1 # n, l, Nzeta, Polarization, NzetaPol > > 5.830 4.597 > 1.000 1.000 > n=5 1 2 # n, l, Nzeta > 7.675 5.545 > 1.000 1.000 > n=4 2 1 # n, l, Nzeta > 3.449 > 1.000 > > > %endblock PAO.Basis > > With this potential and both basis set the parameters (Lattice > constant,cohesive energy and band structure)for tin in diamond form > is well reproduce with the previous literature. But when i draw the band > structure for bct ( beta Sn) phase , the band structure is not match at all > with the literature data. where as cohesive energy and lattice constant is > close to the experimental value. > > > > So please any one give me > an idea that with same basis set and > > pseudopotential file both phases of (alpha and beta )tin are not > reproducible ? > What basis set and pseudopotential is suitable to calculate the beta phase of > Sn ? > > > Kindly suggest me what to do ? > > With best > regards > Suman K Sahoo > Ph.D Student > Deptt. of Chemistry > Visva Bharati, Santiniketan > India > > > > > > > > > > >
