Ian, I wouldn't worry too much, since this is a CG calculation and it has nothing to do with dynamics. That is, it has no physical sense. However, maybe your DM.Tolerance is a bit too high. Try to set it as low as possible. Also, your box seems to be rather small - apparently the minimum distance between the images is 2 angstroms, which is the order of magnitude of a chemical bond. If you want to model the molecule in gas phase (I'm supposing this is what you want to do...) then you should increase the minimum distance between the molecules in all directions - 7 or 8 Angstroms would be enough.
Best regards, Marcos > Siesterers > > I'm modelling the cyanogen molecule, to check my pseudopotentials for C > and N in the molecule by seeing if a CG run gives the same equilibrium > bond lengths as experiment (from the NIST site). > > The simulation converges after about 10 iterations and gives the right > sort of bond lengths. However, initially in the expansion there is a large > expansion of the N molecules. I'm only sampling over the gamma point > (should be good enough for small molecules) but cant figure why the > initial expansion. > > Any ideas? > > Thanks > > Ian Shuttleworth > > ********************************************************************* > > SystemName c2n2 > SystemLabel c2n2 > > NumberOfAtoms 4 > NumberOfSpecies 2 > > %block ChemicalSpeciesLabel > 1 6 C # Species index, atomic number, species label > 2 7 N # Species index, atomic number, species label > %endblock ChemicalSpeciesLabel > > PAO.BasisSize STANDARD > PAO.EnergyShift 300 meV > PAO.BasisType split > > %block Ps.lmax > C 3 > N 3 > %endblock Ps.lmax > > #kgrid_cutoff = brillouin zone sampling paramter (>0 for >gamma point) > > #kgrid_cutoff 20.0 Ang > > #MeshCutoff = equivalent plane wave cut-off for grid > > MeshCutoff 200 Ry > > MaxSCFIterations 50 > DM.MixingWeight 0.3 > DM.NumberPulay 4 > DM.Tolerance 1.d-3 > DM.UseSaveDM > > SolutionMethod diagon > ElectronicTemperature 25 meV > > HarrisFunctional T > WriteCoorStep .true. > WriteForces .true. > WriteMDHistory .true. > > MD.TypeOfRun cg > MD.NumCGsteps 100 > MD.MaxCGDispl 0.1 Ang > MD.MaxForceTol 0.04 eV/Ang > > #AtomicCoordinatesOrigin block is in Bohr > #1 Bohr = 0.52918 angstroem > > %block AtomicCoordinatesOrigin > 5.6691 1.8897 1.8897 > %endblock AtomicCoordinatesOrigin > > LatticeConstant 1.00 Ang > > %block LatticeVectors > 6.000 0.000 0.000 > 0.000 2.000 0.000 > 0.000 0.000 2.000 > %endblock LatticeVectors > > AtomicCoordinatesFormat ScaledCartesian > %block AtomicCoordinatesAndAtomicSpecies > -1.845 0 0 2 > -0.695 0 0 1 > 0.695 0 0 1 > 1.845 0 0 2 > %endblock AtomicCoordinatesAndAtomicSpecies > > > ****************************************************************** > > Input file for C pseudopotential: > > pg C > tm2 2.0 > n=C c=car > 0.0 0.0 0.0 0.0 0.0 0.0 > 1 4 > 2 0 2.00 0.00 > 2 1 2.00 0.00 > 3 2 0.00 0.00 > 4 3 0.00 0.00 > 1.25 1.25 1.25 1.25 0.00 0.00 > > ****************************************************************** > > Input file for N pseudopotential: > > pg N > tm2 2.0 > n=N c=car > 0.0 0.0 0.0 0.0 0.0 0.0 > 1 4 > 2 0 2.00 0.00 > 2 1 3.00 0.00 > 3 2 0.00 0.00 > 4 3 0.00 0.00 > 1.25 1.25 1.25 1.25 0.00 0.00 > -- Dr. Marcos Verissimo Alves Post-Doctoral Fellow Condensed Matter and Statistical Physics Sector International Centre for Theoretical Physics Trieste, Italy -------- I have become so addicted to vi that I try to exit OpenOffice by typing :wq!
