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Electric field gradient; mica; Mössbauer spectra; lattice sum calculations; point charge model; phlogopite

Lattice sum contributions have been calculated at the two octahedral sites in a phlogopite mica assuming a systematic distribution of octahedral cationic charges. This, unlike the case of a random distribution of charges, is able to reproduce broad features of quadrupole doublet spectra in Mössbauer experiments suggesting that the doublet assignments in terms of the two structural sites,M₁ (trans) andM₂(cis), are quite valid. Angle dependence of Mössbauer spectra has also been studied for a ferric-rich phlogopite mica sheet to determine the orientation of the EFG principal axis component and the sign of the quadrupole coupling constant. Quadrupole splitting values and the positive sign of coupling constants match the theoretical predictions quite well but the model fails to predict the observed EFG orientation.

Anjali Krishnamurthy¹ Bipin K Srivastava¹ S Lokanathan¹

1. Department of Physics, University of Rajasthan, Jaipur - 302 004, India

Published

January 1981

Manuscript received

20 September 1980

Manuscript revised

8 December 1980