2022-08-17T22:23:15Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/67692021-08-19T07:09:26Zcom_10261_46com_10261_3col_10261_299
Espinosa, Enrique
2008-08-19T09:24:45Z
2008-08-19T09:24:45Z
1995
Acta Geológica Hispánica, v. 30 (1995). n" 1-3, p. 155-160
1695-6133
http://hdl.handle.net/10261/6769
The electron density model MOLLY, based in a multipolar development
of spherical harmonic functions, has been used to study the
electron density distribution p(r), the electrostatic potential V(,) and the
topology of p(r) of two molecular materials: phosphonc acid and I-arginine
g.i nine phosphate monohydrate.
The study of the phosphorus and oxygen radial functions has been
carried out by means a carefully inspection of the residual maps. Using
three sets of structure factors at several simulated temperatures, the deconvolution
between thermal and electron density parameters is shown
effective. Comparisons between X-(X+N), X-X and theoretical Ab initio
SCF models point out that, in the intermolecular regions, al1 of them
describe V(,) with similar precision.
The difference between the electrostatic potentials developed by a
pseudoisolated molecule of the crystal and a procrystal molecule shows
that crystalline field effects are very small. By inspection of the topo-
Iogy of V(,), hydrogen bonding (HB) seems a limit case of a covalent
bond, which is characterised by positive isopotential lines with sandglass
shapes, as it is found in HB. In H...O region, higher positive values
of V(,) stronger hydrogen bonding interactions happens. Clusters
of pseudoisolated molecules develop the V(,)=O surface around both
molecules and HB regions. This effect point out that, in molecular material~
w ith HBs, crystalline cohesion is a network of electrostatic interactions
which take place inside the volume defined by the zero potential
surface. On the other hand, the p and r values, found at the VZ p critical
point, characterise the HB interaction. They are related to the HB
strength and permit a quantitative approach to its partial covalent character.
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Ácido fosfórico
Fosfato de 1-arginina monohidratado
Densidad electrónica
Difracción de rayos-X
Propiedades electrostáticas,
Estudio de la densidad electrónica y de las propiedades electroestáticas, a partir de experiencias de difracción de rayos-X a baja temperatura y alta resolución, en el ácido fosfórico de 1-arginina monohidratado
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