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.