Hi there, I am working on writing an input generator for PWScf. The input requires that user knows the atomic lattice basis and the Bravais lattice or the exact primitive lattice vectors. I have been playing with SPGLIB in Avogadro to be able to convert unit cell atoms and lattice vectors into the primitive lattice and the atomic basis and I am having trouble getting it to work correctly. Is SPGLIB a good library for this or should I look elsewhere?
I have found that when I run a simple C program linked to Avogardo's libspglib.a, where I use the same atom positions and cell matrix, different results are obtained from those I can print during Avogadro's call to the spglib routines. Further, the Cell Matrix reported back to the gui is very different. For example, the silicon diamond crystal unit cell is a cubic lattice with 8 atoms and has Fd-3m (227) space group symmetry. The 8 atoms in fractional coordinates are listed below. Si 0.00000 0.00000 0.00000 Si 0.00000 0.50000 0.50000 Si 0.50000 0.50000 0.00000 Si 0.50000 0.00000 0.50000 Si 0.75000 0.25000 0.75000 Si 0.25000 0.25000 0.25000 Si 0.25000 0.75000 0.75000 Si 0.75000 0.75000 0.25000 In order to make a usable PWScf input I have to generate the primitive lattice and the atomic basis. A correct PWScf input is show below where PWScf identifies 48 symmetry operations. ATOMIC_POSITIONS Si 0.00 0.00 0.00 Si 0.25 0.25 0.25 CELL_PARAMETERS cubic -0.500000 0.000000 0.500000 0.000000 0.500000 0.500000 -0.500000 0.500000 0.000000 Here "CELL_PARAMETERS" refers to the primitive lattice vectors in fractional coordinates. Since primitive lattice vectors are not unique, there are other possible solutions. All attempts I have made to generate primitive lattice vectors and the atomic basis with SPGLIB do not work in PWScf. At best I have been able make input files that have 8 of the expected 48 symmetry operations. Thanks, Albert ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Avogadro-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/avogadro-devel
