Stephan, Creating a PAO basis set from scratch is a nontrivial exercise even for experts. The way I usually use involves the simplex tetrahedral method, which allows you to vary several parameters at a time and find their optimized values. There is an implementation included with SIESTA.
Look in the Util/Optimizer folder of the siesta source tree. There are some examples there which will allow you to use the simplex method code in a basic manner for a water molecule to optimize basis set parameters. Take a look at the files and study them and run the example calculations. They're pretty quick. From there, it's not a big stretch to apply the principles to arsenic. You will still have to figure out the format of the PAO basis block corresponding to your pseudopotential and desired size of the basis set. You might try using As2S3 or solid arsenic as input, and optimize for bond length and total energy minimization. I'd offer that you might learn more doing it this way. Kind regards, On Wed, Jun 10, 2015 at 7:27 AM, Nick Papior Andersen <[email protected]> wrote: > I would suggest you ask your supervisor/professor (I suspect you have > one?). > > 2015-06-10 16:24 GMT+02:00 Ludwig, Stephan < > [email protected]>: > >> Hello everybody, >> >> >> I'm an absolute beginner in DFT calculations (I'm a Master student) and >> now I have to cope with a material containing Arsenid. >> >> The pseudopotential of As in the database has a semicore state so I have >> to implement the PAO-basis block in the fdf-file. >> >> >> I have no idea how to choose the parameters of this block to obtain >> reasonable results. >> >> I was able to start siesta by using a PAO-basis block which was >> originally designed for iron: >> >> >> %block PAO.Basis # Define Basis set >> As 1 # Species label, number of >> l-shells >> n=3 2 2 # n, l, Nzeta >> 6.000 0.000 >> 1.000 1.000 >> %endblock PAO.Basis >> >> >> >> >> Can anybody please deliver a suitable PAO-basis and a pseudopotential for >> As. >> >> Or can anybody help me to find a suitable PAO-basis for the >> pseudopotential I use. You can find it in the attachment >> >> It would be a great help and I would learn a lot through it >> >> >> Thanks and regards >> >> >> Stephan Ludwig >> >> >> >> > > > -- > Kind regards Nick > -- *Abraham Hmiel, Ph. D.* http://abehmiel.net/about
