Сполуки А3В2С9 (А–К, Rb, Cs, B – As, Sb, Bi; С–СI, Br, І): закономірності зміни та прогноз властивостей

Abstract

The family of the ternary halides A3B2C9 (A – K, Rb, Cs; B – As, Sb, Bi; C – Cl, Br, I) have been classified and analyzed based on the relevant literature data on inorganic chemistry and crystal chemistry, and also based on the experimental results obtained in the laboratory of the Department of Inorganic Chemistry of the Uzhhorod National University over the last three decades. It was shown that the properties of the above compounds, such as crystal symmetry, melting point TM and band gap DE, demonstrate reasonably strong dependencies/correlations on their average nuclear charges Zave; so the above properties are expected to be efficiently predictable for the yet uncharacterized compounds belonging to the same family of chemicals. The chlorides the above type are characterized by Zave £ 31.0, while the bromides and iodides have the Zave values of 31.5 ¸ 42.0 and 43.0 ¸ 58.0, respectively. It has been established that the chemical substitution Cl®Br®I in the above ternary A3B2C9 compounds results in a significant decrease of the DE values, whereas the substitution As®Sb®Bi leads to an increase of the DE band gap for the relevant chlorides and bromides. The highest DE values are observed and expected for the K representatives of the A3B2C9 compounds; the Rb analogs have somewhat smaller values of band gap, while the Cs compounds have the smallest DE values. Single crystals of the K3(Rb3,Cs3)Bi2Cl9 ternary halides with the widest band gaps DE are expected to be suitable for use as the materials for manufacturing the wide-band optical filters (from infrared to visible range of the spectrum); a few representatives of the considered A3B2C9 family could be used as optical cullers. It was also shown that all ternary halides of the above A3B2C9 type crystallize in one of the four possible structural aristotype; and, as with the other considered properties, the crystal symmetry of these halides is dependent on the Zave values. The approach used in this study is simple and straightforward, so it can be recommended for routine investigations of inorganic materials belonging to the same array of chemically and structurally similar compounds. Keywords: ternary halides; melting point, band gap, crystal structures.