Intrinsic nanostructure induced ultralow thermal conductivity yields enhanced thermoelectric performance in Zintl phase EuZnSb.

The Zintl thermoelectric phase EuZnSb has a remarkable combination of high mobility and low thermal conductivity that leads to good thermoelectric performance. The key feature of this compound is a crystal structure that has a Zn-site with a 50% occupancy. Here we use comparison of experimental thermal conductivity measurements and first principles thermal conductivity calculations to characterize the thermal conductivity reduction.

Second Harmonic Generation Susceptibilities from Symmetry Adapted Wannier Functions.

Elucidating the orbital level origin of second harmonic generation (SHG) in materials and identifying the local contributions is a long-standing challenge. We report a first principles approach for the SHG where the contributions from individual orbitals or atoms can be evaluated via symmetry adapted Wannier functions without semiempirical parameters. We apply this method to the common SHG materials KBe_{2}BO_{3}F_{2}, KCaCO_{3}F, and β-BaB_{2}O_{4}, and show that the orbitals on noncentrosymmetric sublattices are responsible for SHG effect and the energies of these orbitals control the magnitude.

Hydrogen Stabilized RhPdH 2D Bimetallene Nanosheets for Efficient Alkaline Hydrogen Evolution.

The design of catalysts with high activity and robust stability for alkaline hydrogen evolution reaction (HER) remains a great challenge. Here, we report an efficient catalyst of two-dimensional bimetallene hydrides, in which H atoms stabilize the rhodium palladium bimetallene. The system exists because of the introduction of H that is in situ chemically released from the formaldehyde solution during the synthesis.

Lone pair effects on ternary infrared nonlinear optical materials.

First-principles studies of the crystal structures, electronic structures and optical properties of noncentrosymmetrical (NCS) K3AsS4, Li3AsS3, Pb9As4S15 and Ag3AsS3 have been performed by means of density functional theory. Via a theoretical method to compute the intensity of the lone pair stereochemical activity of an As-S group, the correlated mechanism among the crystal structures, the stereo-chemical activity of lone pairs on As and the second harmonic generation (SHG) response has been clarified. The results prove that the SHG response is not only attributed to the lone pair stereochemical activity of the As-S group but also related to the direction of the forming layers in the crystal structure arrangement.

Module-Guided Design Scheme for Deep-Ultraviolet Nonlinear Optical Materials.

Design of functional materials with targeted properties is a challenge because of the diversity of their potential structures. The functional performances of materials are mainly determined by the chemistry and electronic structure of modules consisting of local atomic groups with special arrangements. Tetrahedral modules are excellent modules for designing deep-ultraviolet/ultraviolet (UV) nonlinear optical (NLO) materials, but they are rarely favored due to their unpredictable optical anisotropy and second harmonic generation (SHG) response.

Advantageous Units in Antimony Sulfides: Exploration and Design of Infrared Nonlinear Optical Materials.

The exploration of infrared (IR) nonlinear optical (NLO) materials remains attractive because of the urgent requirements in the laser field. Meanwhile, the deepened cognition of structure-property relationships is necessary to help guide the exploration of IR NLO materials. So far, the family of antimony sulfides is an important system with a lot of attention, and a series of antimony sulfides are reported.

A Fluorooxosilicophosphate with an Unprecedented SiO F Species.

The large number and structural beauty of silicates are largely due to the variety of connection mode of SiO tetrahedra. SiO and SiF octahedra are also known and give rise for structural versatility of inorganic silicates. However, to date, the crystal structure of inorganic fluorooxosilicates with oxofluoride SiO F or SiO F species are unknown.

Linear-to-λ-Shape P-O-P Bond Transmutation in Polyphosphates with Infinite (PO) Chain.

A new metal polyphosphate, α-CsBa(PO), exhibiting the first example of a linear P-O-P bond angle in a one-dimensional (PO) chain has been reported. Interestingly, α → β phase transition occurs in CsBa(PO) along with the P-O-P bonds varying from linear to λ-shape, suggesting that α-CsBa(PO) with unfavorable linear P-O-P bonds is more stable at ambient temperature.

ASrPO (A = Rb, Cs): Two Polyphosphates Based on Different Types of P-O Chains and Ring Structures.

Two polyphosphates containing two types of polymerization of the [PO] groups, RbSrPO and CsSrPO, were grown through a spontaneous nucleation method. Single-crystal X-ray diffraction data were collected in order to determine their structures. Interestingly, RbSrPO is the first example of two kinds of [PO] linear chains coexisting in one phosphate structure.

Enhancing optical anisotropy of crystals by optimizing bonding electron distribution in anionic groups.

The response electron distribution anisotropy (REDA) approximation was proposed to analyze the relationship between optical anisotropy and distribution of bonding electrons in compounds. Further, the optical anisotropy of tetrahedral chromophore compounds with common small birefringence can be enhanced and excellent nonlinear optical properties can be obtained by optimizing the distribution.

A New Deep-Ultraviolet Transparent Orthophosphate LiCs2PO4 with Large Second Harmonic Generation Response.

LiCs2PO4, a new deep-ultraviolet (UV) transparent material, was synthesized by the flux method. The material contains unusual edge-sharing LiO4-PO4 tetrahedra. It exhibits a very short absorption edge of λ = 174 nm and generates the largest powder second harmonic generation (SHG) response for deep-UV phosphates that do not contain additional anionic groups, i.

"XA6" octahedra influencing the arrangement of anionic groups and optical properties in inverse-perovskite [B6O10]XA3 (X = Cl, Br; A = alkali metal).

Exploring the effect of microscopic units, which set up the perovsikte framework, is of importance for material design. In this study, a series of borate halides with inverse-perovskite structures [B6O10]XA3 (X = Cl, Br; A = alkali metal) have been studied. It was revealed that the distortion and volume of XA6 octahedra influence the arrangement of anionic groups, which leads to the flexibility of the perovskite-related framework and differences in optical properties.

Active performance of tetrahedral groups to SHG response: theoretical interpretations of Ge/Si-containing borate crystals.

As potential candidates for deep-UV nonlinear optical (NLO) crystals, borosilicates and borogermanates, which contain NLO-active groups such as B-O, Si-O and Ge-O, have fascinated many scientists. The crystal structures, electronic structures and optical properties of seven borates in different B/R (R = Si, Ge) ratios have been studied using DFT methods. Through the SHG-density, we find that besides the recognized contribution of the π-conjugation configuration of BO3 to second harmonic generation (SHG), the tetrahedra have a non-negligible influence.

Three new phosphates with isolated P2O7 units: noncentrosymmetric Cs2Ba3(P2O7)2 and centrosymmetric Cs2BaP2O7 and LiCsBaP2O7.

Three new phosphates, a noncentrosymmetric (NCS) Cs2Ba3(P2O7)2 and centrosymmetric (CS) Cs2BaP2O7 and LiCsBaP2O7, have been synthesized from high-temperature solutions for the first time. Analysis of the structures determined by single-crystal X-ray diffraction showed that although the three compounds contained isolated P2O7 units, they yielded different three-dimensional (3D) networks: Cs2Ba3(P2O7)2 crystallized in the NCS Orthorhombic space group P212121, Cs2BaP2O7 in the CS monoclinic space group P21/n, and LiCsBaP2O7, having an identical stoichiometry with Cs2BaP2O7, crystallized in monoclinic space group, P21/c. Structural comparisons suggested the differences between their 3D frameworks to be due to differences between the sizes and coordination environments of the cations.

Li3AlSiO5: the first aluminosilicate as a potential deep-ultraviolet nonlinear optical crystal with the quaternary diamond-like structure.

Deep-ultraviolet (deep-UV) nonlinear optical (NLO) crystals play a crucial role in modern laser frequency conversion technology. Traditionally, the exploration of deep-UV NLO crystals is mainly focused on borates, while, the use of phosphates recently opened up a novel and promising non-boron pathway for designing new deep-UV NLO crystals. Extending this pathway to aluminosilicates led to the discovery of Li3AlSiO5, the first NLO crystal in this system.