5. Results

5.5 Bond properties

Further insight on the crystal binding can be gained by analyzing and representing the value of representative scalar fiels on the basin surface.

The representation of the electron density provides information regarding the zones where the electrons accumulate. Those accumulation regions correspond to the presence of bond critical points. By using the same color scale for each basin, the relative importance of the different types of bonds can be revealed. In the case of CsBeI3, for instance Fig. 5.5 (left) is accumulated more intensely on the I-I bond zone than in the Be-I or Cs-I bonds.

The strength of the bond, however, is better determined by representing the laplacian of the electron density (i.e. ). Fig. 5.5 (right) shows that, even if the accumulation of density is larger on the I-I bonds, the curvature of the electron density is larger at the Be-I bonds. Analogous results occur for all perovskites. The topological analysis thus recovers the classical image of the M-X bonds being the main responsible for the structural stability of the perovskite.

Fig. 5.5 Representation of the electron density (left) and its laplacian (right) on the surface of the ionic basins. The color scale goes linearly from blue on the relative minima to red on the relative maxima. The basins have been calculated using critic and rendered with Geomview.

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Page dates: May 20, 1996 (creation), June 7, 1996 (last update).
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Copyright © 1996 Víctor Luaña, Aurora Costales and Angel Martín Pendás.