A theoretical comparison of C54 and C49 TiSi2 Surfaces is presented, using ab initio plane-wave ultrasoft pseudopotential method based on generalized gradient approximation (GGA). The different surface energies of TiSi2 have not only been calculated out, but the preferential formation of C49 phase in solid-state reaction could be explained by smaller surface energies and Poisson's ratio of C49 TiSi2 as well. As for polar C54 TiSi2(100) and C49 TiSi2(010) surfaces, the Si termination surfaces are more stable. (c) 2005 Elsevier B.V. All rights reserved.