Margarita S. Avdontceva, Andrey P. Shablinskii, Maria G. Krzhizhanovskaya, Sergey V. Krivovichev, Andrey A. Zolotarev, Vladimir N. Bocharov, Natalia S. Vlasenko, Evgenia Yu. Avdontseva, Victor N. Yakovenchuk
{"title":"Nefedovite, Na5Ca4(PO4)4F: thermal evolution, phase transition and crystal structure refinement","authors":"Margarita S. Avdontceva, Andrey P. Shablinskii, Maria G. Krzhizhanovskaya, Sergey V. Krivovichev, Andrey A. Zolotarev, Vladimir N. Bocharov, Natalia S. Vlasenko, Evgenia Yu. Avdontseva, Victor N. Yakovenchuk","doi":"10.1007/s00269-024-01276-7","DOIUrl":null,"url":null,"abstract":"<div><p>Nefedovite, Na<sub>5</sub>Ca<sub>4</sub>(PO<sub>4</sub>)<sub>4</sub>F, has been investigated by in situ high-temperature powder (30–690 °C) and single crystal (27–827 °C) X-ray diffraction and Raman spectroscopy. Nefedovite is tetragonal, space group <i>I</i>-4, <i>a</i> = 11.6560(2), <i>c</i> = 5.4062(2) Å, <i>V</i> = 734.50(2) Å<sup>3</sup> (<i>R</i><sub><i>1</i></sub> = 0.0149). Nefedovite is a 1<i>D</i> antiperovskite, since its crystal structure contains chains of corner-sharing anion-centered [FCa<sub>4</sub>Na<sub>2</sub>]<sup>9+</sup> octahedra. The chains are parallel to the <i>c</i> direction. Nefedovite is stable up to 727 °C and undergoes a displacive phase transition in the temperature range 277–327 <i>°</i>C. With increasing temperature, the PO<sub>4</sub> tetrahedra in the crystal structure of nefedovite gradually rotate around the imaginary fourfold inversion axes aligning the O2<sup>…</sup>O3 edge parallel to [110], which ultimately leads to the appearance of the mirror plane perpendicular to the <i>c</i> direction and the change of space group from <i>I</i>-4 (82) to <i>I</i>4/<i>m</i> (87). The crystal structure of nefedovite expands strongly anisotropically with the direction of the maximum thermal expansion oriented perpendicular to the chains of anion-centered octahedra. The information-based structural complexity analysis demonstrates that both low- and high-temperature modifications of nefedovite are structurally simple with the <i>I</i><sub>G,total</sub> value less than 100 bits per unit cell. The structural complexity decreases along the phase transition, which is typical for displacive phase transitions.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-024-01276-7","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Nefedovite, Na5Ca4(PO4)4F, has been investigated by in situ high-temperature powder (30–690 °C) and single crystal (27–827 °C) X-ray diffraction and Raman spectroscopy. Nefedovite is tetragonal, space group I-4, a = 11.6560(2), c = 5.4062(2) Å, V = 734.50(2) Å3 (R1 = 0.0149). Nefedovite is a 1D antiperovskite, since its crystal structure contains chains of corner-sharing anion-centered [FCa4Na2]9+ octahedra. The chains are parallel to the c direction. Nefedovite is stable up to 727 °C and undergoes a displacive phase transition in the temperature range 277–327 °C. With increasing temperature, the PO4 tetrahedra in the crystal structure of nefedovite gradually rotate around the imaginary fourfold inversion axes aligning the O2…O3 edge parallel to [110], which ultimately leads to the appearance of the mirror plane perpendicular to the c direction and the change of space group from I-4 (82) to I4/m (87). The crystal structure of nefedovite expands strongly anisotropically with the direction of the maximum thermal expansion oriented perpendicular to the chains of anion-centered octahedra. The information-based structural complexity analysis demonstrates that both low- and high-temperature modifications of nefedovite are structurally simple with the IG,total value less than 100 bits per unit cell. The structural complexity decreases along the phase transition, which is typical for displacive phase transitions.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)