Hi Marcos The k-point sampling would in general be different. Are both calculations well converged in k points?
Emilio On Aug 21, 2015, at 1:33 AM, Marcos Veríssimo Alves wrote: > Hi all, > > I am running some calculations for a 3D structure made of carbon, using > Siesta 3.2-pl-5. The executable was compiled with > > gfortran using mpif90 -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions > -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic > > however, I am running the code serially, since the structures I'm working > with have 4 or 8 atoms. > > My structure has a monoclinic unit cell of 4 atoms, and when I run an SCF for > the atomic positions, I get appreciable forces along the basal (xy) plane of > the cell, which seemed a bot strange to me. When I transformed the 4-atom > monoclinic cell into an 8-atom orthorhombic one, with exactly the same > structure, the forces along the basal plane were around 10^-5 eV/Ang, which > was what I expected. > > Has anyone experienced that kind of problem? I'd like to stress that the > problem is not the atomic positions: upon replicating the 4-atom supercell > properly, I get exactly the same geometry of the 8-atom orthorhombic cell. > Would anyone have a hint as to why this happens? > > Best regards, > > Marcos > > -- Emilio Artacho CIC nanoGUNE Consolider, and Cavendish Laboratory, University of Cambridge Tolosa Hiribidea 76, E-20018 Donostia - San Sebastián, Spain, [email protected], +34 943 574039, http://theory.nanogune.eu
