A new nonlinear optical silicate carbonate K2Ca[Si2O5](CO3) with a hybrid structure of kalsilite and soda-like layered fragments

作者：Belokoneva Elena L^*; Stefanovich Sergey Yu; Volkov Anatoly S; Dimitrova Olga V

来源：Solid State Sciences, 2016, 60: 23-27.

DOI：10.1016/j.solidstatesciences.2016.08.003

• K, Ca silicate carbonate
• Hydrothermal synthesis
• Single crystal structure
• Structural relations
• Optical nonlinearity

Single crystals of a new silicate carbonate, K2Ca[Si2O3](CO3), have been synthesized in a multi components hydrothermal solution with a pH value close to neutral and a high concentration of a carbonate mineralizer. The new compound has an axial structure (s.g. P6(3)22) with unit cell parameters a = 5.04789 (15), c = 17.8668 (6) angstrom. Pseudosymmetry of the structure corresponds to s.g. P6(3)/mmc which is broken only by one oxygen position. The structure consists of two layered fragments: one of the type of the mineral kalsilite (KAlSiO4) and the other of the high-temperature soda-like alpha-Na2CO3, Ca substituting for Na. The electro-neutral layer K-2[Si2O5] (denoted K) as well as the layer Ca(CO3) (denoted S) may separately correspond to individual structures. In K2Ca[Si2O5](CO3) the S-K layers are connected together via Ca-O interactions between Ca atoms from the carbonate layer and apical O atoms from the silicate one, and also via K-O interlayer interactions. A hypothetical acentric structure, sp.gr. P-62c, is predicted on the basis of the order-disorder theory. It presents another symmetrical option for the arrangement of K-layers relative to S-layers. The K,Ca-silicate-carbonate powder produces a moderate SHG signal that is two times larger that of the alpha-quartz powder standard and close to other silicates with acentric structures and low electronic polarizability. (C ) 2016 Elsevier Masson SAS.

• 出版日期2016-10