Spin-Density Distribution in Cu<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cl</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>·2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">D</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>O

The spin-density distribution in antiferromagnetic Cu${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}2${\mathrm{D}}_{2}$O has been investigated at 1.7\ifmmode^\circ\else\textdegree\fi{}K by neutron diffraction measurements. No appreciable concentrations of spin density were found except those localized about the ${\mathrm{Cu}}^{++}$ positions. The Fourier maps used in analyzing the neutron data did disclose a markedly aspherical distribution for the ${\mathrm{Cu}}^{++}$ spin density, however. A satisfactory explanation for the asphericity was obtained by consideration of the ground-state wave function of ${\mathrm{Cu}}^{++}$ in an orthorhombic crystalline field. The resulting wave function was found to consist of an admixture of two $d\ensuremath{\gamma}$ orbitals, about $90%({x}^{2}\ensuremath{-}{y}^{2})$ and $10%(3{z}^{2}\ensuremath{-}{r}^{2})$. The neutron study also confirms the existence of a weak antiferromagnetic spin component, as predicted theoretically by Moriya. The form factor for this component is quite anomalous, however, indicating that it does not arise from a simple canting of the ionic moment.

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