Abstract
Polarized neutron diffraction experiments on the deuterated ammonium nickel Tutton salt at 2.00 and 4.20 K and a magnetic field of 4.60 T yielded 483 unique magnetic structure factors based upon the more intense Bragg nuclear reflections. A supporting experiment on the hydrogenous compound yielded 100 unique magnetic structure factors. These structure factors were used in a least-squares refinement of a model based upon atomic orbital populations located on the nickel, oxygen and deuterium atoms and in the Ni—O bond centre of the Ni(OD
2
)
2+
6
octahedron. The refinement (R
w
= 0.061,
X
= 1.98) gave averaged populations as follows: Ni : t
2g
= – 0.06, e
g
= 1.64,4s = 0.38; O : (sp
2
)
1
= 0.04, (sp
2
)
2, 3
= 0.01, p
π
= 0.00; D: Is = 0.00; Ni—O: ‘overlap ’ = —0.05 spins. The Ni—OD
2
interactions show more covalent spin transfer than was seen for the similar Mn—OH
2
system and the ‘overlap’ population is correspondingly higher. These interactions resemble strongly those in the Ni—ND
3
bond of Ni(ND
3
)
4
(NO
2
)
2
. A feature of the difference from the Mn(OH
2
)
2+
ion is the absence of spin in the hydrogen atoms, and this correlates with the essentially zero spin in the Ni-t
2g
orbitals. Evaluation of the mixing parameters of a simple m. o. model, A
σ
= 0.49, S
σ
= 0.09, leads to values which resemble those for the Ni—ND
3
bonding in Ni(ND
3
)
4
(NO
2
)
2
. Spin polarization effects are negligible
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2
O)
2+
6
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