> 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
