(V2O5)n gas-phase clusters (n=1-12) compared to V2O5 crystal:: DFT calculations

Stable structures of neutral (V2O5)(n) clusters (n = 1-5, 8, 10, and 12) are determined by density functional calculations (BP86 functional with a double-zeta (V)/triple- (O) valence basis set augmented by polarization functions). Comparison is made with calculations for the periodic structure of solid V2O5. The most stable structure of the smallest cluster is doubly O-bridged, OV-O-2-VO2, and by 184 kJ/mol VO2.5 less stable than the periodic bulk structure. From the tetrahedral V4O10 structure on (41 kJ/mol VO2.5 above the crystal energy) polyhedral cage structures are the most stable isomers: trigonal prism (V6O12), cube (V8O20), pentagonal prism (V10O25), 16-hedron (V16O40), dodecahedron (V20O50), and truncated octahedron (V24O60). The polyhedra have vanadyl groups at the apexes and bridging oxygen atoms on the edges. Differently from the crystal structure, vanadium is 4-fold coordinated and 3-fold coordinated oxygen is avoided. The energies relative to the periodic solid are 22.1, 12.4, 9.4, 5.5, 3.3, and 3.4 kJ/mol VO2.5, respectively. Structures that correspond to fragments cut out of the crystal structure (examined up to n = 8) are significantly less stable. The IR spectra of cage-type-structures will show bands in the 1040-1080 cm(-1) and in the 800-925 cm(-1) regions (terminal V=O-(1) and bridging V-O-(2)-V, respectively), but not between 650 and 750 cm(-1) or around 500 cm(-1) (V-O-2((2))-V double bridges and triply coordinated oxygen, respectively).