We present a systematic theoretical investigation on the work functions of five closed surfaces of metal hexaborides including LaB6, BaB6, CaB6, CeB6, SrB6 and SmB6. The results are in a close agreement with available experimental measurements and previous theoretical findings. The variations of the work function display a good trend. For BaB6, CaB6 and SrB6, the increasing order is [Formula: see text](100) [Formula: see text](110) [Formula: see text](211) [Formula: see text](112) [Formula: see text](111). For CeB6, LaB6, and SmB6, the sequence is somewhat different: [Formula: see text](100) [Formula: see text](211) [Formula: see text](112) [Formula: see text](110) [Formula: see text](111). The work function changes with the metal hexaborides series have also been discussed. The increasing order of the (100) surface is LaB6(100) [Formula: see text] CeB6(100) [Formula: see text] SmB6(100) [Formula: see text] SrB6(100) [Formula: see text] BaB6(100) [Formula: see text] CaB6(100). The orders for the (110) and (111) surface are similar: BaB6(110, 111) [Formula: see text] SrB6(110, 111) [Formula: see text] LaB6(110, 111) [Formula: see text] CeB6(110, 111) [Formula: see text] CaB6(110, 111) [Formula: see text] SmB6(110, 111). For the (112) and (211) surface, the sequence is BaB6(112, 211) [Formula: see text] LaB6(112, 211) [Formula: see text] CeB6(112, 211) [Formula: see text] SrB6(112, 211) [Formula: see text] SmB6(112, 211) [Formula: see text] CaB6(112, 211).
