Polarized electronic absorption spectra of colourless chalcocyanite, CuSO₄, with a survey on crystal fields in Cu²⁺ minerals

Author(s)

Manfred Wildner, Gerald Giester, Monika Kersten, Klaus Langer

Abstract

Polarized electronic absorption spectra of colourless chalcocyanite, CuSO₄, have been measured using microscope-spectrometric techniques. The spectra are characterized by a structured and clearly polarized band system in the near-infrared spectral range with components centred at 11,720, 10,545, 9,100, and 7,320 cm^-1, which have been assigned to crystal field d-d transitions of Cu²⁺ cations in pseudo-tetragonally elongated CuO₆ polyhedra with point symmetry C_i ((Formula presented.)). The polarization behaviour is interpreted based on a D₂(C₂″) pseudo-symmetry. Crystal field calculations were performed for the actual triclinic point symmetry by applying the Superposition Model of crystal fields, as well as in terms of a 'classic' pseudo-tetragonal crystal field approach yielding the parameters Dq_(eq) = 910, Dt = 395, and Ds = 1,336 cm^-1, corresponding to a cubically averaged Dq_cub = 679 cm^-1. A comparative survey on crystal fields in Cu²⁺ minerals shows that the low overall crystal field strength in chalcocyanite, combined with a comparatively weak pseudo-tetragonal splitting of energy levels, is responsible for its unique colourless appearance among oxygen-based Cu²⁺ minerals. The weak crystal field in CuSO₄ can be related to the lower position of the SO₄

^2- anion compared to, e.g. the H₂O molecule in the spectrochemical series of ligands.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Technische Universität Berlin

Journal

Physics and Chemistry of Minerals

Volume

41

Pages

669-680

No. of pages

12

ISSN

0342-1791

DOI

https://doi.org/10.1007/s00269-014-0681-1

Publication date

05-2014

Peer reviewed

Yes

Austrian Fields of Science 2012

105116 Mineralogy, 105113 Crystallography, 1030 Physics, Astronomy

Keywords

ASJC Scopus subject areas

General Materials Science, Geochemistry and Petrology

Portal url

https://ucrisportal.univie.ac.at/en/publications/cdb1fd96-2109-40d5-8994-6e79ddbbc719