(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) ar e determined by density functional calculations (BP86 functional with a dou ble-zeta (V)/triple- (O) valence basis set augmented by polarization functi ons). Comparison is made with calculations for the periodic structure of so lid V2O5. The most stable structure of the smallest cluster is doubly O-bri dged, OV-O-2-VO2, and by 184 kJ/mol VO2.5 less stable than the periodic bul k 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-hedro n (V16O40), dodecahedron (V20O50), and truncated octahedron (V24O60). The p olyhedra have vanadyl groups at the apexes and bridging oxygen atoms on the edges. Differently from the crystal structure, vanadium is 4-fold coordina ted 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, respect ively. Structures that correspond to fragments cut out of the crystal struc ture (examined up to n = 8) are significantly less stable. The IR spectra o f cage-type-structures will show bands in the 1040-1080 cm(-1) and in the 8 00-925 cm(-1) regions (terminal V=O-(1) and bridging V-O-(2)-V, respectivel y), but not between 650 and 750 cm(-1) or around 500 cm(-1) (V-O-2((2))-V d ouble bridges and triply coordinated oxygen, respectively).