Electron density dictionary (rhoCIF) version 1.0.1
Category ATOM_RHO_MULTIPOLE
Name:'_atom_rho_multipole_[rho]'
Definition:
This category contains information about the multipole
coefficients used to describe the electron density.
High-resolution X-ray diffraction methods enable the
determination of the electron density distribution in
crystal lattices and molecules, which in turn allows for a
characterization of chemical interactions (Coppens, 1997;
Koritsanszky & Coppens, 2001). This is accomplished by
the construction of a mathematical model of the charge
density in a crystal and then by fitting the parameters of
such a model to the experimental pattern of diffracted
X-rays. The model on which this dictionary is based
is the so-called multipole formalism proposed by Hansen
& Coppens (1978). In this model, the electron density in
a crystal is described by a sum of aspherical "pseudoatoms"
where the pseudoatom density has the form defined in the
_atom_rho_multipole_* items. Each pseudoatom density
consists of terms representing the core density, the spherical
part of the valence density and the deviation of the valence
density from sphericity. The continuous electron density in the
crystal is then modelled as a sum of atom-centred charge
distributions. Once the experimental electron density has been
established, the "atoms in molecules" theory of Bader (1990)
provides tools for the interpretation of the density
distribution in terms of its topological properties.
Ref: Bader, R. F. W. (1990). Atoms in molecules: a quantum
theory. Oxford University Press.
Coppens, P. (1997). X-ray charge densities and chemical
bonding. Oxford University Press.
Hansen, N. K. & Coppens, P. (1978). Acta Cryst. A34,
909-921.
Koritsanszky, T. S. & Coppens, P. (2001). Chem. Rev. 101,
1583-1621.
Example:
Example 1 - Multipole coefficients for the nickel ion in
[Ni(H3L)][NO3][PF6], [H3L =
N,N',N''-tris(2-hydroxy-3-methylbutyl)-1,4,7-triazacyclononane]
[G.T. Smith et al. (1997). J. Am. Chem. Soc. 119, 5028-5034].
loop_
_atom_rho_multipole_atom_label
_atom_rho_multipole_coeff_Pv
_atom_rho_multipole_coeff_P00
_atom_rho_multipole_coeff_P11
_atom_rho_multipole_coeff_P1-1
_atom_rho_multipole_coeff_P10
_atom_rho_multipole_coeff_P20
_atom_rho_multipole_coeff_P21
_atom_rho_multipole_coeff_P2-1
_atom_rho_multipole_coeff_P22
_atom_rho_multipole_coeff_P2-2
_atom_rho_multipole_coeff_P30
_atom_rho_multipole_coeff_P31
_atom_rho_multipole_coeff_P3-1
_atom_rho_multipole_coeff_P32
_atom_rho_multipole_coeff_P3-2
_atom_rho_multipole_coeff_P33
_atom_rho_multipole_coeff_P3-3
_atom_rho_multipole_coeff_P40
_atom_rho_multipole_coeff_P41
_atom_rho_multipole_coeff_P4-1
_atom_rho_multipole_coeff_P42
_atom_rho_multipole_coeff_P4-2
_atom_rho_multipole_coeff_P43
_atom_rho_multipole_coeff_P4-3
_atom_rho_multipole_coeff_P44
_atom_rho_multipole_coeff_P4-4
_atom_rho_multipole_kappa
_atom_rho_multipole_kappa_prime0
_atom_rho_multipole_kappa_prime1
_atom_rho_multipole_kappa_prime2
_atom_rho_multipole_kappa_prime3
_atom_rho_multipole_kappa_prime4
Ni2+(1) 2.38(4) 0.32(4) 0.00 0.00 -0.02(1)
0.00(2) 0.00 0.00 0.00 0.00
-0.08(1) 0.00 0.00 0.00 0.00 0.06(1) -0.04(1)
0.05(1) 0.00 0.00 0.00 0.00 -0.20(1) 0.08(1)
0.00 0.00
1.04(1) 0.44(1) 0.44 1.15(4) 0.44 1.15
|
Type: null
Category: category_overview
