Structure of Na3OCl

The Antiperovskite-Type Oxychalcogenides Ae3 Q[GeOQ3 ] (Ae = Ba, Sr; Q = S, Se) with Large Second Harmonic Generation Responses and Wide Band Gaps

Oxychalcogenides capable of exhibiting excellent balance among large second-harmonic generation (SHG) response, wide band gap (Eg ), and suitable birefringence (Δn) are ideal materials class for infrared nonlinear optical (IR NLO) crystals. However, rationally designing a new high-performance oxychalcogenide IR NLO crystal still faces a huge challenge because it requires the optimal orientations of the heteroanionic groups in oxychalcogenide. Herein, a series of antiperovskite-type oxychalcogenides, Ae3 Q[GeOQ3 ] (Ae = Ba, Sr; Q = S, Se), which were synthesized by employing the antiperovskite-type Ba3 S[GeS4 ] as the structure template. Their structures feature novel three-dimensinoal frameworks constructed by distorted [QAe6 ] octahedra, which are further filled by [GeOQ3 ] tetrahedra to form antiperovskite-type structures. Based on the unique antiperovskite-type structures, the favorable alignment of the polarizable [GeOQ3 ] tetrahedra and distorted [QAe6 ] octahedra have been achieved. These contribute the ideal combination of large SHG response (0.7-1.5 times that of AgGaS2 ), wide Eg (3.52-4.10 eV), and appropriate Δn (0.017-0.035) in Ae3 Q[GeOQ3 ]. Theoretical calculations and crystal structure analyses revealed that the strong SHG and wide Eg could be attributed to the polarizable [GeOQ3 ] tetrahedra and distorted [QAe6 ] octahedra. This research provides a new exemplification for the design of high-performance IR NLO materials.

Hydro-flux synthesis and crystal structure of Tl3IO

Single-crystals of thallium(I) iodide oxide Tl3IO were obtained as by-product in a hydro-flux synthesis at 473 K for 10 h. A potassium hydroxide hydro-flux with a water-base molar ratio of 1.6 and the starting materials TlNO3, RhI3 and Ba(NO3)2 was used, resulting in a few black needle-shaped crystals. X-ray diffraction on a single-crystal revealed the hexa-gonal space group P63/mmc (No. 194) with lattice parameters a = 7.1512 (3) Å and c = 6.3639 (3) Å. Tl3IO crystallizes as hexa-gonal anti-perovskite (anti-BaNiO3 type) and is thus structurally related to the alkali-metal halide/auride oxides M 3 XO (M = K, Rb, Cs; X = Cl, Br, I, Au). The oxygen atoms center thallium octa-hedra. The [OTl6] octa-hedra share trans faces, forming a linear chain along [001]. Twelve thallium atoms surround each iodine atom in an [ITl12] anti-cubocta-hedron. Thallium and iodine atoms together form a hexa-gonal close-sphere packing, in which every fourth octa-hedral void is occupied by oxygen.

Antiperovskites with Exceptional Functionalities

ABX₃ perovskites, as the largest family of crystalline materials, have attracted tremendous research interest worldwide due to their versatile multifunctionalities and the intriguing scientific principles underlying them. Their counterparts, antiperovskites (X₃ BA), are actually electronically inverted perovskite derivatives, but they are not an ignorable family of functional materials. In fact, inheriting the flexible structural features of perovskites while being rich in cations at X sites, antiperovskites exhibit a diverse array of unconventional physical and chemical properties. However, rather less attention has been paid to these "inverse" analogs, and therefore, a comprehensive review is urgently needed to arouse general concern. Recent advances in novel antiperovskite materials and their exceptional functionalities are summarized, including superionic conductivity, superconductivity, giant magnetoresistance, negative thermal expansion, luminescence, and electrochemical energy conversion. In particular, considering the feasibility of the perovskite structure, a universal strategy for enhancing the performance of or generating new phenomena in antiperovskites is discussed from the perspective of solid-state chemistry. With more research enthusiasm, antiperovskites are highly anticipated to become a rising star family of functional materials.

Periodic ab initio calculation of nuclear quadrupole parameters as an assignment tool in solid-state NMR spectroscopy: applications to 23Na NMR spectra of crystalline materials

Periodic ab initio HF calculations using the CRYSTAL code have been used to calculate (23)Na NMR quadrupole parameters for a wide range of crystalline sodium compounds including Na(3)OCl. An approach is developed that can be used routinely as an alternative to point-charge modelling schemes for the assignment of distinct lines in (23)Na NMR spectra to specific crystallographic sodium sites. The calculations are based on standard 3-21 G and 6-21 G molecular basis sets and in each case the same modified basis set for sodium is used for all compounds. The general approach is extendable to other quadrupolar nuclei. For the 3-21 G calculations a 1:1 linear correlation between experimental and calculated values of C(Q)((23)Na) is obtained. The 6-21 G calculations, including the addition of d-polarisation functions, give better accuracy in the calculation of eta((23)Na). The sensitivity of eta((23)Na) to hydrogen atom location is shown to be useful in testing the reported hydrogen-bonded structure of Na(2)HPO(4).

Determination of the (Na+) Sternheimer antishielding factor by 23Na NMR spectroscopy on sodium oxide chloride, Na3OCl

The (Na+) Sternheimer antishielding factor gammainifinity (Na+) was determined by 23Na NMR spectroscopy on sodium oxide-chloride, Na3OCl. The quadrupolar coupling constant of the sodium ion in Na3OCI was determined to QCC = 11.34 MHz, which presents the largest coupling constant of a sodium nucleus observed so far. Applying a simple point charge model, the largest principal value of the electric field gradient at the sodium site was calculated to V(zz) = -6.76762 x 10(20) V/m2. From these values we calculated the (Na+) Sternheimer antishielding factor to gammainifinity (Na+)= -5.36. In sodium oxide, Na2O, we observed an isotropic chemical shift of deltaCS = 55.1 ppm, referenced to 1 M aqueous NaCI (delta = 0 ppm).