Structural and Spectroscopic Studies of NaCuCr2(PO4)3: A Noncentrosymmetric Phosphate Belonging to the α‑CrPO4‑Type Compounds

• Published in: Inorganic chemistry Vol. 60; no. 11; pp. 7803 - 7814
• Main Authors: Souiwa, Khalifa, Lebraud, Eric, Gayot, Marion, Weill, Francois, Mauvy, Fabrice, Avdeev, Maxim, Chtourou, Radhouane, Hidouri, Mourad, Toulemonde, Olivier
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07-06-2021
• Subjects: Chemical Sciences; Inorganic chemistry; Material chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c00296

An electron and joint neutron and X-ray diffraction study of the synthetic copper/chromium phosphate NaCuCr2(PO4)3 (NaCuP) is reported. A noncentrosymmetric Imm2 space group belonging to the well-known α-CrPO4 type is observed contrary to what is reported in NaMCr2(PO4)3 (M = Co and Ni) phosphates. The structural model is validated by bond valence sum analysis and charge-distribution (CHARDI) calculations and supported by complementary infrared and Raman spectroscopy investigations. Both Raman spectroscopy and theoretical study by deformation density approach further suggest the presence of Cu2+ (3d9) and Cr2+ (3d4) Jahn–Teller polaron effects as a key factor to the centro Imma to noncentrosymmetric Imm2 phase change.