Institute of Mineralogy, Petrology, & Economic Geology, Tohoku University^* Quantum Beam Center, National Institute for Materials Science, Japan^**
○Koichi Momma^* Fujio Izumi^**

Though many structure-drawing programs are available nowadays, only few can deal with both structural models and electron/nuclear densities resulting from diffraction data and simulation. Then, we have developed a new computer program, VESTA (Visualization for Electronic and STructural Analysis), for three-dimensional visualization of pixel data and structural models. VESTA represents crystal structures as ball-and-stick, space-filling, polyhedral, wireframe, stick, dot-surface, and thermal-ellipsoid models. Electron/nuclear densities, wave functions, and electrostatic potentials are visualized as isosurfaces, bird's-eye views, and two-dimensional maps. VESTA has a feature of surface colorization to show the electrostatic-potential value at each point on isosurfaces. Translucent isosurfaces and/or slices can be overlapped with a structural model. VESTA allows us to handle a virtually unlimited number of objects such as atoms, bonds, polyhedra, and polygons on isosurfaces. Drawing boundaries can be specified with lattice planes and ranges along x, y, and z axes. General equivalent positions can be transformed from conventional to non-conventional settings using a transformation matrix. Interatomic distances and bond angles on which restraints are imposed in Rietveld analysis with RIETAN-FP are easily visualized through close cooperation between VESTA and ORFFE.