Relative stability of low-index V₂O₅surfaces: a density functional investigation

Abstract

Ab initio density functional calculations of the structural and electronic properties of V(2)O(5) bulk and its low-index surfaces are presented. For the bulk oxide and the (010) surface (the natural cleavage plane) a good agreement with experiment and with earlier ab initio calculations is found. For the first time, the investigations are extended to other low-index surfaces: (001) and (100). On both surfaces, termination conserving a bulk-like stoichiometry is preferred, but-in contrast to the (010) surface-a strong structural relaxation takes place. Relaxation reduces the surface energy from 1.16 to 0.48 J m(-2) for the (001) and from 0.61 to 0.55 J m(-2) for the (100) surface. Although the relaxed surface energies are still one order of magnitude higher than calculated for the (010) surface (0.047 J m(-2)), the Wulff construction demonstrates that (001) and (100) surfaces contribute about 15% of the total surface area of a V(2)O(5) crystallite, indicating a non-negligible role in the catalytic activity of V(2)O(5).

Role of van der Waals bonding in the layered oxideV2O5: First-principles density-functional calculations

“…[5][6][7][8][9][10][11][12] The in-plane lattice parameters, in the present paper called a and b ͑but in parts of the literature called a and c͒, are found to be close to the experimental values. [8][9][10][11][12][13] Ganduglia-Pirovano and Sauer 12 carried out GGA calculations using PW91 ͑Ref. 45͒ with PAW, emphasizing convergence and accuracy.…”

“…1 In recent years V 2 O 5 has also been used with intercalating Li ions for high-capacity solid-state batteries. [2][3][4][5] The applied research and industrial focus on catalysis and batteries involving V 2 O 5 has led to a substantial amount of atomic-scale theory studies focusing on the V 2 O 5 bulk [5][6][7][8][9][10][11][12] and its surfaces. [12][13][14][15][16] The bulk of V 2 O 5 has a stacked structure.…”

“…Previous atomic-scale calculations that were based on densityfunctional theory ͑DFT͒ with the popular semilocal generalized gradient approximations ͑GGAs͒ have often failed in arriving at the experimentally known value of the lattice parameter in the stacking direction of the layers. [8][9][10][11][12][13] This is believed to happen because GGA does not describe the van der Waals ͑vdW͒ forces, 17 and because these are expected to play an important role in binding the layers in V 2 O 5 bulk. 12 In several GGA-based V 2 O 5 surface or vacancy studies this deficiency of GGA was either ignored or worked around by imposing the experimentally obtained lattice parameter or unit-cell volume.…”

Electronic Structure of Unsaturated V2O5(001) and (100) Surfaces: Ab Initio Density Functional Theory Studies

“…For the V 2 O 5 (100) netplane the ''t1'' termination, which is characterized by unsaturated V atoms together with two kinds of oxygen sites (O(1) and O(2)), has been chosen as the most stable from among four possible cuts of this surface [44] (Fig. 2b) were performed.…”

“…Also MD (Molecular Dynamic) simulations (based on electrostatic interactions) of the thermal stability of the V 2 O 5 structure have indicated the (010) netplane as the most stable among the three low-index surfaces of V 2 O 5 [43]. Theoretical investigations of the stability of (100) and (001) netplanes perpendicular to the (010) surface [44] have also shown that although their steadiness is an order of magnitude lower, their content in the structure of a standard crystal reaches 7.2 and 8.3%, respectively. For this reason, they should not be neglected.…”