Ab initio quantum-mechanical modeling and (110) surfaces of zabuyelite (Li2CO3)

Bulk and (0 0 1) (1 0 1) and (1 1 0) slab geometry optimizations of zabuyelite (Li2CO3) were performed at Hartree-Fock (HE) and DFT levels. The (0 0 1) and (1 0 1) slabs showed an higher surface relaxation with respect to the (1 1 0) slab. The CO3 groups in the top surface laver of (0 0 1) and (1 0 1) slabs are strongly tilted with respect to their position in the bulk. tending to arrange parallel to the respective faces. On the contrary, a modest surface relaxation was observed for the (1 1 0) slab. The surface energies (gamma) for relaxed and unrelaxed (0 0 1) (10 1) and (1 1 0) faces, were determined at the HE and DFT levels. The values of the surface energy for the relaxed faces are: (gamma(001)) = 160(HF)-180(DFT), (gamma(01)) = 260-280 and (gamma(101)) = 570-590 erg/cm(2). For the unrelaxed faces the values of the surface energy result to be higher: (gamma(001)) = 248-255, (gamma(101)) = 392-399, (gamma(101)) = 674-697 erg/cm(2). Therefore, the stability order of relaxed and unrelaxed surfaces reads: (0 0 1 ) < (1 0 1) < (1 1 0), as results from both HE and DFT calculations. (C) 2007 Elsevier B.V. All rights reserved.