[xcrysden] On k-space path selection

[Tone Kokalj]

> I am a newbie to XCrysDen, and I have a few basic questions about the
> k-point path selection feature on XCrysDen. I have an XSF file I enerated
> from the output of an ab initio program unsupported by XCrysDen. To my
> delight I found that the program gives me the Brillouin Zone (BZ)
> automatically with high-symmetry points indicated. The questions are:
>
> 1) Is this general, or does it come from a set of pre-defined BZs? I mean,
> if I enter any crystal structure and ask for the BZ, how are the
> high-symmetry points found?

The labeling of the k-points is supported by a few Bravais lattice
types, and is based on a lookup table of Peter Blaha: see last part
of the file $XCRYSDEN_TOPDIR/Tcl/kLabels.tcl

In order for this labelling to work, there should be info about the
Bravais lattice type in the XSF file. This is achieved by replacing the
"CRYSTAL" keyword by:

DIM-GROUP
3 igroup

where "3" specifies 3 dimensional periodicity, and igroup the
lattice type, in particular:

1 ... primitive
2 ... A centered
3 ... B centered
4 ... C centered
5 ... face-centered (i.e. fcc)
6 ... body-cetered (i.e. bcc)
7 ... rhombohedral
8 ... hexagonal
9 ... trigonal

>
> 2) This one is not really related to XCrysDen, but I feel I might get some
> help here. Given three reciprocal space vectors, is there a way to use the
> Bilbao Crystallographic Server to tell me to which space group my lattice
> belongs to? This way, I could get the labels for the high-symmetry points
> of the BZ.

I don't know.

Regard, Tone