def write_kpts_vasp(kpts):
    """
    Write a list of kpoints to a vasp-formatted KPOINTS file.
    """
    output = "Supercell_k-points_from_primitive_cell\n"
    output += str(len(kpts))+"\n"
    output += "reciprocal\n"
    for i in range(len(kpts)):
        for j in range(3):
            output += str(kpts[i,j])+" "
        output += "1.0\n"
    return output