Electrostatic energy calculations of diaspore (α AlOOH), goethite (α FeOOH) and groutite (α MnOOH)

R. F. Giese Jr., S. Weller and P. Datta

Abstract

The electrostatic energy of diaspore has been calculated as a function of the hydroxyl-hydrogen position and the ionic charge on the aluminum, oxygen and hydrogen. The position of the hydrogen atom determined previously by neutron diffraction coincides with the minimum in the eletrostatic energy for all charge combinations which satisfy the equations x = 3t, y = −2t, z = t, where 0 ≤ t ≤ 1, x = aluminum charge, y = oxygen charge, z = hydrogen charge.

Computation of the electrostatic energy from the Born-Haber cycle suggests that the fully ionized charges (t = 1) are the best values. Electrostatic-energy calculations for goethite show that the hydrogen atom is also found near the minimum in the electrostatic energy when the iron, oxygen and hydrogen are fully ionized. This approach has been used to predict the hydrogen position in the groutite structure.

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Zeitschrift für Kristallographie – Crystalline Materials offers a place for researchers to present results of their crystallographic studies. The journal includes theoretical as well as experimental research. It publishes Original Papers, Letters and Review Articles in manifold areas of crystallography.

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