Theoretical studies of the EPR parameters and local structures for Ni³⁺ and Cu²⁺ centers in MgNH₄PO₄·6H₂O

ABSTRACT

The electron paramagnetic resonance (EPR) parameters of the impurity Ni³⁺ (and Cu²⁺) in MgNH₄PO₄·6H₂O (MAPH) are theoretically studied from the perturbation formulas for 3d⁷ (and 3d⁹) ions under orthorhombically compressed (and elongated) octahedra, respectively. In the above formulas, the related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way. In the calculation model, the impurity Ni³⁺ and Cu²⁺ ions were ascribed to occupy the host octahedral Zn²⁺ site, the required crystal-field parameters are correlated with the local structures of the impurity Ni³⁺ and Cu²⁺ in MAPH. Based on calculation, the compressed [NiO₆]^9- cluster (and elongated [CuO₆]^10- cluster) are found to suffering the axial compression of 0.051 Å (and elongation of 0.125 Å) along z-axis, meanwhile, the planar bonds are found to experience the relative variations of 0.028 Å (and 0.05 Å), respectively, due to the Jahn–Teller effect. The theoretical EPR parameters based on the above lattice distortions agree well with the experimental data, and the local structures of the Ni³⁺ and Cu²⁺ in MAPH are discussed.

KEYWORDS:

• Local structures
• EPR
• MgNH₄PO₄·6H₂O (MAPH)
• Ni³⁺
• Cu²⁺

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financially supported by Chinese Natural Science Foundation (grants 11764028 and 12064027), Foundation of Jiangxi Educational Committee (GJJ180524), Graduate student innovation project YC2020-S548 and Open Project of National Demonstration Center for Experimental College Physics Education (SY2013).

Notes on contributors

Yadong Li

Yadong Li is graduate student in Nanchang Hangkong University, her research interests include the investigation on electron paramagnetic resonance (EPR) spectroscopy of transition metal ions in materials.

Huaming Zhang

Huaming Zhang is Professor in the Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, P.R. China. He got His PhD degree in University of Electronic Science and Technology of China, Chengdu. His research interests include the investigation on electron paramagnetic resonance (EPR) spectroscopy of transition metal ions in materials, preparation and performance control of electrocatalyst.

Di Gui

Di Gui is Lecturer in the Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, P.R. China. He got his PhD degree in Huazhong University of Science and Technology of China, Wuhan. His research interests include the investigation on mechanical and optical properties of metal inorganic-organic hybrid frameworks.

Jian-Zhuang Yin

Jian-Zhuang Yin is lecturer in the National Demonstration Center for Experimental College Physics Education, Nanchang Hangkong University, P.R. China. He got his PHD degree in Education from Sichuan University, Chengdu, P.R. China. His area of research interest is quantum transport.

W.B. Xiao

W. B. Xiao is a full Professor in the Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, P.R. China. In 2008，he obtained his PhD degree in microelectronics and solid state electronics from the Institute of semiconductors, Chinese Academy of Sciences, China. His research interests concentrate on semiconductor physics and photoelectric detection.