Crystal structure and spin gap state of CaV2O5

The crystal structure and electronic state of CaV2O5 have been explored through X-ray four-circle diffraction, magnetization, and ESR measurements. The crystal at 297 K is orthorhombic with space group Pmmn and the lattice constants are a = 11.351 (2) Angstrom, b = 3.604 (1) Angstrom, c = 4.893 (1) Angstrom, and Z = 2. Full-matrix least-squares refinement gives the final values of R = 0.044 and R(w) = 0.034 for 880 independent reflections with R(int) = 0.041. The structure is described in terms of VO5 pyramids which are joined by sharing edges and corners to form characteristic V zigzag chains along the b-axis. Along the a-axis, the zigzag chains are linked by sharing corners, leading to a quasi-two-dimensional layer. This compound has a spin-singlet ground state with a gap of 660 K and g = 1.96. (C) 1996 Academic Press.