First-principles study of Ni2P (0001) surfaces

We report ab initio calculations of the structural and electronic properties of Ni2P (0001) surfaces. The geometric relaxation results in a rumpling surface structure. Both Ni3P2- and Ni3P-terminated surfaces can be formed, but the surface prefers to be terminated by Ni3P2. The calculated partial density of states of the Ni and P atoms agrees well with previous theoretical and experimental results. The work function is predicted to be 5.22 and 4.75 eV for the Ni3P2- and Ni3P-terminated surfaces, respectively. The simulated scanning tunneling microscopy images of Ni2P (0001) surfaces with positive bias voltage reproduce the main features of the experimental observations. The bright spots correspond well to the P sites with hexagonal symmetry.