bkpts

The bkpts-file contains information on the nearest neighbors of the k-points. Here is an example:

   8
     1     2      0   0   0
     1     3      0   0   0
     1     5      0   0   0
     1     8      0   0   0
     1     2      0   0  -1
     1     3      0  -1   0
     1     5     -1   0   0
     1     8     -1  -1  -1
     2     1      0   0   0
     2     4      0   0   0
     2     6      0   0   0
     2     1      0   0   1
     2     7      0   0   1
     2     4      0  -1   0
     2     6     -1   0   0
     2     7     -1  -1   0
     3     1      0   0   0
     3     4      0   0   0
     3     7      0   0   0
     3     1      0   1   0
     3     6      0   1   0
     3     4      0   0  -1
     3     7     -1   0   0
     3     6     -1   0  -1
     4     2      0   0   0
     4     3      0   0   0
     4     8      0   0   0
     4     2      0   1   0
     4     3      0   0   1
     4     5     -1   0   0
     4     8     -1   0   0
     4     5      0   1   1
     5     1      0   0   0
     5     6      0   0   0
     5     7      0   0   0
     5     1      1   0   0
     5     4      1   0   0
     5     6      0   0  -1
     5     7      0  -1   0
     5     4      0  -1  -1
     6     2      0   0   0
     6     5      0   0   0
     6     8      0   0   0
     6     2      1   0   0
     6     5      0   0   1
     6     3      0  -1   0
     6     8      0  -1   0
     6     3      1   0   1
     7     3      0   0   0
     7     5      0   0   0
     7     8      0   0   0
     7     3      1   0   0
     7     5      0   1   0
     7     2      0   0  -1
     7     8      0   0  -1
     7     2      1   1   0
     8     1      0   0   0
     8     4      0   0   0
     8     6      0   0   0
     8     7      0   0   0
     8     1      1   1   1
     8     4      1   0   0
     8     6      0   1   0
     8     7      0   0   1

At the top, the number of nearest neighbors of each k-point is given. Here, it is 8, which is the number of nearest neighbors in the bcc-lattice. The rest of the file is composed of 5 columns. The first column gives the index of a k-point. The second column gives the index of a nearest neighbor of that k-point, if the nearest neighbor lies in the first Brillouin zone. If a nearest neighbor is not located in the first Brillouin zone, then a translation by a reciprocal lattice vector is applied to it to move it into the first Brillouin zone. The index of the nearest neighbor refers then to a k-point in the first Brillouin zone and the last three columns specify the reciprocal lattice vector needed for the translation.