First-principles study of Ti3AC2 (A = Si, Al) (001) surfaces

We have systematically studied the mechanical properties and surface properties of (1 x 1) Ti(3)AC(2) (A = Si, Al) (001) using the density functional theory (DFT). The calculated cleavage energy for each possible cleavage site shows that Ti-Si and Ti-Al are the weakest layers, while the Ti-C layer is the strongest one. It reveals that the main difference between Ti3SiC2 and Ti3AlC2 is that the Ti-Si bond is stronger than the Ti Al bond. This shows the different mechanical and surface properties between them. The surface rumpling and surface energy of Ti3SiC2 and Ti3AlC2 are calculated. The study shows that the cleavage energy affects both the surface rumpling and the surface energy. The higher the cleavage energy, the larger the surface energy and surface rumpling. Furthermore, the most stable surface structures are predicted for different experimental conditions. The predicted surface structures agree with the available experimental results. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.