I'll bet your lattice vectors are quite large and this is the reason you are getting insufficient memory errors (larger volume=more mesh points=more memory needed). Try reducing the lattice vectors in the vacuum direction. You probably only need 4 or 5 times the thickness of your slab of vacuum.
Hope this helps. Daniel Backlund Texas Tech University - Physics ________________________________ On Jul 14, 2010 7:01 PM, tarang mungole <[email protected]> wrote: Sorry for the way I asked the question.... Thanks for your reply....well I checked the geometry in Xcrysden and it showed the correct picture(if I replicate the picture in all directions) . Actually apart from this , I calculated the energies of the slabs extending upto infinity in 2 directions and restricted in the z direction by giving a big vacuum space in the unit cell(I guess this is the cluster you are talking about). I used Ni infinite slabs, then i used Ni infinite slabs with adatoms and calculated the enery differences and the differences were like 10KeV! Well in this case, I had put a big vacuum space in all the 3 directions and it says that virtual memory is not enough InitMesh: MESH = 500 x 500 x 500 = 125000000 InitMesh: Mesh cutoff (required, used) = 100.000 104.475 Ry forrtl: severe (41): insufficient virtual memory On Wed, Jul 14, 2010 at 1:10 PM, N H <[email protected]<mailto:[email protected]>> wrote: Did you checked the output geometry to see whether this is really the geometry you want or not? Another question: Do you like to calculate a Slab or a cluster? It seems that your calculation is set to a Cluster. It is also not clear which energy you would like to calculate. Remember that absolute total energies calculated with SIESTA ( or any other method ) have no meaning in itself - once the energy reference is arbitrary. You have to compare it with the energy of another well-defined system and establish energy differences. Just to give an idea, I calculate ZnO slabs with more or less 40 atoms ( including some molecules adsorbed ) and the total energies are something like -35KeV ... and it is normal. A last tip: The people here in this list use to be very friendly and helpful. So there is no need to urging someone to solve the problem you posted with "It's very urgent!!". Everybody here is open to help each other, but everybody here also have urgent stuff to do besides answering the SIESTA mail-L. If you want help, please ask it nicely. Best Regards NH On Wed, Jul 14, 2010 at 12:01 PM, Juan Beltran <[email protected]<mailto:[email protected]>> wrote: I find that your system do not have that many C atoms, how does the energy compare with a pure Ni system?, still large?. Compare also the energy you obtain for that big supercell with the pure FCC Ni system (1 atom may do). The difference should be due to the presence of vacum along the three directions and I guess it should be less that 100eV from the 50KeV you obtain from the large system. Juan On 07/14/2010 12:45 AM, tarang mungole wrote: I have made a slab with FCC configuration and I want to calculate the energy of the slab!! The slab contains 5 layers of Nickel atoms and a carbon atom on the top of it. I just want to calculate the energy of this system!!! ....I made a supercell having 5X5X5 lattice constants in each direction ( 5a 5a 5a 60 60 60) and then gave a BIG vaccum space so that the nearby Replicated supercells do not interact.(Is this a correct concept??????) . The problem is that the energies that i get are very large!!!! about -50KeV!! Can any body tell what is wrong in my fdf input file....it's very urgent!! ---------------------------------------------------FDF FILE---------------------------------------------------------------------------------------------------------------------------------------------- %block ChemicalSpeciesLabel 1 28 Ni 2 6 C %endblock ChemicalSpeciesLabel SaveRho .true. LatticeConstant 1.0 Ang %block LatticeParameters 99.6 99.6 99.6 60. 60. 60. %endblock LatticeParameters %block AtomicCoordinatesOrigin 0.000 0.000 0.000 %endblock AtomicCoordinatesOrigin MD.TypeOfRun CG MD.NumCGSteps 0 AtomicCoordinatesFormat Fractional %block AtomicCoordinatesAndAtomicSpecies 0.000 0.000 0.000 1 0.025 0.000 0.000 1 0.050 0.000 0.000 1 0.075 0.000 0.000 1 0.000 0.025 0.000 1 0.025 0.025 0.000 1 0.050 0.025 0.000 1 0.075 0.025 0.000 1 0.000 0.050 0.000 1 0.025 0.050 0.000 1 0.050 0.050 0.000 1 0.075 0.050 0.000 1 0.000 0.075 0.000 1 0.025 0.075 0.000 1 0.050 0.075 0.000 1 0.075 0.075 0.000 1 0.000 0.000 0.025 1 0.025 0.000 0.025 1 0.050 0.000 0.025 1 0.075 0.000 0.025 1 0.000 0.025 0.025 1 0.025 0.025 0.025 1 0.050 0.025 0.025 1 0.075 0.025 0.025 1 0.000 0.050 0.025 1 0.025 0.050 0.025 1 0.050 0.050 0.025 1 0.075 0.050 0.025 1 0.000 0.075 0.025 1 0.025 0.075 0.025 1 0.050 0.075 0.025 1 0.075 0.075 0.025 1 0.000 0.000 0.050 1 0.025 0.000 0.050 1 0.050 0.000 0.050 1 0.075 0.000 0.050 1 0.000 0.025 0.050 1 0.025 0.025 0.050 1 0.050 0.025 0.050 1 0.075 0.025 0.050 1 0.000 0.050 0.050 1 0.025 0.050 0.050 1 0.050 0.050 0.050 1 0.075 0.050 0.050 1 0.000 0.075 0.050 1 0.025 0.075 0.050 1 0.050 0.075 0.050 1 0.075 0.075 0.050 1 0.000 0.000 0.075 1 0.025 0.000 0.075 1 0.050 0.000 0.075 1 0.075 0.000 0.075 1 0.000 0.025 0.075 1 0.025 0.025 0.075 1 0.050 0.025 0.075 1 0.075 0.025 0.075 1 0.000 0.050 0.075 1 0.025 0.050 0.075 1 0.050 0.050 0.075 1 0.075 0.050 0.075 1 0.000 0.075 0.075 1 0.025 0.075 0.075 1 0.050 0.075 0.075 1 0.075 0.075 0.075 1 0.000 0.000 0.100 1 0.025 0.000 0.100 1 0.050 0.000 0.100 1 0.075 0.000 0.100 1 0.000 0.025 0.100 1 0.025 0.025 0.100 1 0.050 0.025 0.100 1 0.075 0.025 0.100 1 0.000 0.050 0.100 1 0.025 0.050 0.100 1 0.050 0.050 0.100 1 0.075 0.050 0.100 1 0.000 0.075 0.100 1 0.025 0.075 0.100 1 0.050 0.075 0.100 1 0.075 0.075 0.100 1 0.033 0.033 0.125 2 0.100 0.000 0.000 1 0.100 0.025 0.000 1 0.100 0.050 0.000 1 0.100 0.075 0.000 1 0.100 0.100 0.000 1 0.100 0.000 0.025 1 0.100 0.025 0.025 1 0.100 0.050 0.025 1 0.100 0.075 0.025 1 0.100 0.100 0.025 1 0.100 0.000 0.050 1 0.100 0.025 0.050 1 0.100 0.050 0.050 1 0.100 0.075 0.050 1 0.100 0.100 0.050 1 0.100 0.000 0.075 1 0.100 0.025 0.075 1 0.100 0.050 0.075 1 0.100 0.075 0.075 1 0.100 0.100 0.075 1 0.100 0.000 0.100 1 0.100 0.025 0.100 1 0.100 0.050 0.100 1 0.100 0.075 0.100 1 0.100 0.100 0.100 1 0.000 0.100 0.000 1 0.025 0.100 0.000 1 0.050 0.100 0.000 1 0.075 0.100 0.000 1 0.000 0.100 0.025 1 0.025 0.100 0.025 1 0.050 0.100 0.025 1 0.075 0.100 0.025 1 0.000 0.100 0.050 1 0.025 0.100 0.050 1 0.050 0.100 0.050 1 0.075 0.100 0.050 1 0.000 0.100 0.075 1 0.025 0.100 0.075 1 0.050 0.100 0.075 1 0.075 0.100 0.075 1 0.000 0.100 0.100 1 0.025 0.100 0.100 1 0.050 0.100 0.100 1 0.075 0.100 0.100 1 %endblock AtomicCoordinatesAndAtomicSpecies SolutionMethod diagon Thnx in advance!!
