that's true. If you don't specify anything, the default values of LatticeConstant and LatticeVectors will be used (see the manual). Look through the h2o.fdf input file as an example of specifying the water molecule (in examples directory of siesta distribution). If you run this example you'll the the following line in the output file:
siesta: System type = molecule siesta determines the type of the system automatically depending on the specified lattice. Check this line to be sure you're calculating a cluster not a periodic lattice. On 15/08/07, Mauro F. S. Ribeiro Jr. <[EMAIL PROTECTED]> wrote: > Dear Ian, > > You need to specify the size of the box you want to consider, and the final > energy shall depend on this size - which depends on the size of your > cluster. So, try to write the atomic positions in cartesian coordinates, > setting the lattice constant to unit, and the cell vectors, say, much larger > than the cluster (5 times or more, you can converge this, though as bigger > the box, as slow the calculation becomes). > > M. > > > 2007/8/15, Ian Shuttleworth <[EMAIL PROTECTED]>: > > If the block LatticeVectors is not specified does siesta assume that the > > unit is not repeating, that is, it's just a free standing molecule or > > cluster and that there are no adjacent cells? > > > > Has anyone got any experience of modelling these finite units (in > > particular clusters) and comments about how periodicity is treated by > > siesta in these systems? > > > > Thanks > > > > Ian Shuttleworth > > > > > > -- > ********************************************************************* > Mauro F. Soares Ribeiro Jr. > Institute of Physics, University of São Paulo, BRAZIL > "We can help with virtually anything larger than quarks > and smaller than galaxies." > ********************************************************************* -- Yurko Natanzon PhD Student Henryk Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences ul. Radzikowskiego 152, 31-342 Kraków, Poland Email: [EMAIL PROTECTED], [EMAIL PROTECTED]
