Dear Andrei, >this seems to be a too "loosely defined" question; >"will be Siesta accurate enough" with which basis, cutoffs etc.?

basis set DZP mesh cutoff 200 Ry I did test calculations for Si(100) (unreconstructed and unrelaxed) surface energy in Siesta, the Esurf is very close to published values obtained in VASP (error less than 1 meV/A2). So I am quite sure about this. Kind regards Ruslan 2009/6/4 <apost...@uni-osnabrueck.de> > > Dear Siesta users, > > > > recently Andrei Postnikov wrote a small tutorial on Siesta > > http://www.home.uni-osnabrueck.de/apostnik/Lectures/SIESTA-tuto.pdf > > > > He wrote: > > "one cannot a priori expect equally good performance of basis over > > a large range of bond lengths and, say, pressures: as the pressure is > > varying, the “completeness” > > or “variational freedom” of basis in the region of chemically relevant, > > under a given pressure, bond > > lengths do vary; consequently the calculated pressure/energy curve may > > slightly differ from that > > obtained in a “benchmark” FLAPW calculation." > > > > A good test would be to compare bulk VASP and Siesta calculations and > > deside > > if calculation > > in Siesta is accurate enough at some particular pressure. Unfortunately > we > > don't have VASP here. > > > > My question is (+/- 10%) of the equlibrium lattice constants of Si and Ge > > are Ok for Siesta? > > Will be Siesta accurate enough to calculate surface energy with an error > > of about 1 meV/A2 ? > > Dear Ruslan, > this seems to be a too "loosely defined" question; > "will be Siesta accurate enough" with which basis, cutoffs etc.? > It would demand a more careful study, volume curve vs. volume curve, > in the spirit or Junquera's tests of basis - Fig.2 of PRB64, 235111. > If you don't have VASP nor WIEN2k, install ABINIT or PWSCF > which should be good enough for Si and Ge. > The surface energy is another philosophical question > (the issue of wrong asymptotics on the surface? Using different > pseudo?) - I think this has been addressed in some of quite early > Siesta papers. > > Best regards > > Andrei Postnikov >