Eur. Phys. J. D (2014) 68: 313
https://doi.org/10.1140/epjd/e2014-50359-0

Regular Article

Theoretical studies of the EPR parameters and local structures for Cu²⁺ centres in a (CH₃)₂NH₂Al(SO₄)₂·6H₂O crystal

¹ Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, Nanchang 330063, P.R. China
² Key Laboratory of Space Active Opto-Electronics Technology, Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, Shanghai 200083, P.R. China

^a e-mail: huamingzhang66@gmail.com

Received: 7 May 2014
Received in final form: 22 July 2014
Published online: 23 October 2014

Abstract

Local structure and electron paramagnetic resonance (EPR) parameters (the g factors, g_i, and the hyperfine structure constants A_i, i = x, y, z) for the impurity Cu²⁺ centres in a (CH₃)₂NH₂Al(SO₄)₂·6H₂O (DMAAS) crystal are theoretically investigated by using the high-order perturbation formulas of these parameters for a 3d⁹ ion in an orthorhombically elongated octahedron. The related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way. From the studies, the four planar Cu²⁺-O²⁻ bond lengths are found to experience the relative variation δR ( ≈0.033 and 0.063 Å) along the X- and Y-axes, while the two parallel bond lengths may undergo relative elongation ΔZ (≈0.058 and 0.052 Å) along the C₂ axis for the studied Cu²⁺ centres I and II, respectively, due to the Jahn-Teller effect. The theoretical EPR parameters based on the above local lattice distortions agree well with the experimental data. The results are discussed.