Inorganic Crystals Research Articles

Stereochemically Active Lone Pair Leads to Birefringence in the Vacancy Ordered Cs3Sb2Cl9 Perovskite Single Crystals.

Stereochemically active lone pair (SCALP) cations are attractive units for realizing optical anisotropy. Antimony(III) chloride perovskites with the SCALP have remained largely unknown to date. We synthesized a new vacancy ordered Cs3Sb2Cl9 perovskite single crystals with SbCl6 octahedral linkage containing the SCALP. Remarkably, all-inorganic halide perovskite Cs3Sb2Cl9 single crystals exhibit an exceptional birefringence of 0.12 ± 0.01 at 550 nm. The SCALP brings a large local structural distortion of the SbCl6 octahedra promoting birefringence optical responses in Cs3Sb2Cl9 single crystals. Theoretical calculations reveal that the considerable hybridization of Sb 5s and 5p with Cl 3p states largely contribute to the SCALP. Furthermore, the change in the Sb-Cl-Sb bond angle creates distortion in the SbCl6 octahedral arrangement in the apical and equatorial directions within the crystal structure incorporating the required anisotropy for the birefringence. This work explores pristine inorganic halide perovskite single crystals as a potential birefringent material with prospects in integrated optical devices.

Automated analysis of surface facets: the example of cesium telluride

High-throughput screening combined with ab initio calculations is a powerful tool to explore technologically relevant materials characterized by complex configurational spaces. Despite the impressive developments achieved in this field in the last few years, most studies still focus on bulk materials, although the relevant processes for energy conversion, production, and storage occur on surfaces. Herein, we present an automatized computational scheme that is capable of calculating surface properties in inorganic crystals from first principles in a high-throughput fashion. After introducing the method and its implementation, we showcase its applicability, focusing on four polymorphs of Cs2Te, an established photocathode material for particle accelerators, considering slabs with low Miller indices and different terminations. This analysis gives insight into how the surface composition, accessible through the proposed high-throughput screening method, impacts the electronic properties and, ultimately, the photoemission performance. The developed scheme offers new opportunities for automated computational studies beyond bulk materials.

Electrical polarization switching of perovskite polariton laser

Abstract Optoelectronic and spinoptronic technologies benefit from flexible and tunable coherent light sources combining the best properties of nano- and material-engineering to achieve favorable properties such as chiral lasing and low threshold nonlinearities. In this work we demonstrate an electrically wavelength- and polarization-tunable room temperature polariton laser due to emerging photonic spin–orbit coupling. For this purpose, we design an optical cavity filled with both birefringent nematic liquid crystal and an inorganic perovskite. Our versatile growth method of single CsPbBr3 inorganic perovskite crystals in polymer templates allows us to reach strong light–matter coupling and pump-induced condensation of exciton–polaritons resulting in coherent emission of light. The sensitivity of the liquid crystal to external voltage permits electrical tuning of the condensate energy across 7 nm; its threshold power, allowing us to electrically switch it on and off; and its state of polarization sweeping from linear to locally tilted circularly polarized emission.

Pressure-Driven Piezoelectric Sensors and Energy Harvesting in Biaxially Oriented Polyethylene Terephthalate Film.

This study reports the possibility of using biaxially oriented polyethylene terephthalate (BOPET) plastic packaging to convert mechanical energy into electrical energy. Electricity is generated due to the piezoelectricity of BOPET. Electricity generation depends on the mechanical deformation of the processing aids (inorganic crystals), which were found and identified by SEM and EDAX analyses as SiO2. BOPET, as an electron source, was assembled and tested as an energy conversion and self-powered mechanical stimuli sensor using potential applications in wearable electronics. When a pressure pulse after pendulum impact with a maximum stress of 926 kPa and an impact velocity of 2.1 m/s was applied, a voltage of 60 V was generated with short-circuit current and charge densities of 15 μAcm-2 and 138 nCm-2, respectively. Due to the orientation and stress-induced crystallization of polymer chains, BOPET films acquire very good mechanical properties, which are not lost during their primary usage as packaging materials and are beneficial for the durability of the sensors. The signals detected using BOPET sensors derived from pendulum impact and sieve analyses were also harvested for up to 80 cycles and up to 40 s with short-circuit voltages of 107 V and 95 V, respectively. In addition to their low price, the advantage of sensors made from BOPET plastic packaging waste lies in their chemical resistance and stability under exposure to oxygen, ultraviolet light, and moisture.

Emerging van der Waals Dielectrics of Inorganic Molecular Crystals for 2D Electronics.

In the landscape of continuous downscaling metal-oxide-semiconductor field-effect transistors, two-dimensional (2D) semiconductors with atomic thinness emerge as promising channel materials for ultimate scaled devices. However, integrating compatible dielectrics with 2D semiconductors, particularly in a scalable way, remains a critical challenge that hinders the development of 2D devices. Recently, 2D inorganic molecular crystals (IMCs), which are free of dangling bonds and possess excellent dielectric properties and simplicity for scalable fabrication, have emerged as alternatives for gate dielectric integration in 2D devices. In this Perspective, we start with the introduction of structure and synthesis methods of IMCs and then discuss the explorations of using IMCs as the dielectrics, as well as some remaining relevant issues to be unraveled. Moreover, we look at the future opportunities of IMC dielectrics in 2D devices both for practical applications and fundamental research.

Organic Phosphorescent Hopper-Shaped Microstructures.

Hopper-shaped microcrystals, an unusual type of crystal with a large specific surface area, are promising for use in catalysis, drug delivery, and gas sensors. In contrast to well-studied inorganic hopper-shaped crystals, organic phosphorescent concave hopper-shaped microstructures are rarely reported. This study reports the synthesis of two types of organic stepped indented hopper-shaped microstructures with efficient room temperature phosphorescence (RTP) using a liquid phase self-assembly strategy. The formation mechanism is attributed to the interfacial instability induced by the concentration gradient and selective etching. Compared with flat microstructures, the stepped indented hopper-like RTP microstructures exhibit high sensitivity to oxygen. This work also demonstrates that packing the photochromic material into the concave hopper "vessel" effectively controls the switch of phosphorescence from energy transfer, expanding the potential applications of phosphorescent materials.

Antimony Doped Hybrid Zinc Halide Crystals with Tunable Light Emission and Long‐Term Stability

AbstractAs a class of emerging photoluminescent materials, hybrid halide crystals have drawn research attention for their potential application in the fields of light‐emitting, security, and waveguide. Nevertheless, hybrid halide crystals containing antimony with long‐term stability and tunable light emission are still increasingly in demand. In this work, serial new hybrid halide crystals (BZA)2ZnCl4·2H2O:xSb3+ (x = 0–0.2, x represents the reaction ratio) and (BZA)2SbCl5 are synthesized (BZA = 2,4‐diamino‐6‐phenyl‐1,3,5‐triazine). In (BZA)2ZnCl4·2H2O:xSb3+ crystals, Sb3+ cations replace partial Zn2+ cations to form [SbCl4]− tetrahedron. Red light emission caused by the substitution of Sb3+ for Zn2+ enhances as the doping rate increases, resulting in the tunable emission from light blue to pink and finally to dark red. There are two kinds of Sb3+ in (BZA)2SbCl5 crystal. Sb(1) has a sixfold coordination with Cl to form a [Sb(1)Cl5]∞ 1D zigzag chain. Sb(2) atom adopts a fivefold coordination with Cl and is separated from each other by BZA+ cations. (BZA)2SbCl5 crystal shows bright orange‐yellow light emission with a photoluminescence quantum yield of 45%. Moreover, the organic–inorganic hybrid metal halide crystals containing antimony have excellent long‐term stability, with phase and luminescence keeping nearly unchanged after more than six months in ambient air.

Predicting melting temperature of inorganic crystals via crystal graph neural network enhanced by transfer learning

The melting temperature, a crucial material property, is particularly challenging to measure accurately for inorganic crystals. The data-driven approach emerges as a potential solution, although its effectiveness is hindered by the limitation of available data. To counter this challenge, we implement transfer learning, leveraging a vast computational database of atomization energy. We first pre-train a geometric-information-enhanced crystal graph neural network (GeoCGNN) using atomization energies of approximately 36,000 materials that are computed by the density functional theory. Subsequently, the pre-trained model is fine-tuned using melting temperatures measured for 799 crystals, encompassing 83 elements, ranging from unary to quaternary systems. This transfer learning strategy decreases the root mean square error from 407 to 218 K, attesting to a marked improvement in prediction accuracy. Furthermore, transfer learning significantly mitigates error variability across unary, binary, and ternary (or higher-order) systems, thereby enhancing the reliability of predictions across a broader range of crystals. We also show that transfer learning allows effective task adaptation by leveraging representation learned from pre-training. Therefore, it can achieve better prediction performance even with a limited number of data for predicting melting points.

Biomineralization-Inspired Confined-Space Fabrication of Polyimide Aerogels.

The biomineralization process endows biominerals with unique hierarchically porous structures and physical-chemical properties by filling the restricted microreaction space with amorphous phases before the growth of inorganic crystals. In this paper, a confined-space fabrication method inspired by biomineralization for preparing hierarchically porous polyimide (PI) aerogels and PI-derived carbon aerogels is introduced. The confined structure is established through a self-assembly method of vacuum impregnation and ultrasound-assisted freeze-drying. The hierarchically porous structure is controlled by adjusting the structure characteristics of the confined space and secondary aerogels. Subsequently, a variety of performance demonstrations are conducted to demonstrate the mechanical properties and application prospects in the fields of thermal insulation and electromagnetic shielding of the prepared aerogel.

Emerging lead-free all inorganic perovskite single crystals K7Bi3X16 (X = Cl, Br) toward photodetector application.

Lead-free inorganic perovskites have attracted intensive attention in the field of photodetectors owing to their high stability, non-toxicity, and remarkable photoelectric characteristics. Herein, we designed and developed a series of thus-far unreported lead-free all inorganic perovskite single crystals, K7Bi3X16 (X = Cl, Br). In particular, we resorted to cooling crystallization and intercalated K+ to inorganic Bi-Br and Bi-Cl frameworks as inorganic A-site cations, obtaining zero-dimensional (0D) K7Bi3X16 (X = Cl, Br) perovskite single crystals, which display suitable bandgaps, excellent electron mobility and low trap-state density, as analysed by experimental characterization and density functional theory (DFT) calculations. Accordingly, the vertical structure K7Bi3Br16 photodetector can achieve a fast ON/OFF switch under the irradiation of 395 nm light. When the light intensity is 5 mW cm-2 and the voltage is 3 V, the responsivity is calculated to be 0.052 mA W-1. The above characteristics make K7Bi3Br16 a promising material for fabricating ultraviolet photodetectors.

When topology meets geometry: topological motifs and uniformity of atomic sublattices in inorganic crystals

We have analyzed topological motifs of whole crystal structures and unconnected non-metal sublattices in 967 borides, 721 carbides, 899 nitrides and 927 silicides of metals within the periodic net model....

Prediction methods for Phonon Transport Properties of Inorganic Crystals: from Traditional Approaches to Artificial Intelligence

In inorganic crystals, phonons are the elementary excitations describing the collective atomic motions. The study of phonons plays an important role in terms of understanding thermal transport behavior and acoustic...

First principles study on polarization and piezoelectric properties of group substitution regulated lead-free organic perovskite ferroelectrics

Organic ferroelectrics are desirable for the applications in the field of wearable electronics due to their eco-friendly process-ability, mechanical flexibility, low processing temperatures, and lightweight. In this work, we use five organic groups as substitution for organic cation and study the effects of organic cations on the structural stability, electronic structure, mechanical properties and spontaneous polarization of metal-free perovskite <i>A</i>-NH<sub>4</sub>-(PF<sub>6</sub>)<sub>3</sub> (<i>A</i> = MDABCO, CNDABCO, ODABCO, NODABCO, SHDABCO) through first-principles calculations. Firstly, the stabilities of the five materials are calculated by molecular dynamics simulations, and the energy values of all systems are negative and stable after 500 fs, which demonstrates the stabilities of the five materials at 300 K. The electronic structure calculation shows that the organic perovskite materials have wide band gap with a value of about 7.05 eV. The valence band maximum (VBM) and Cconduction band minimum (CBM) are occupied by different elements, which is conductive to the separation of electrons and holes. We find that organic cations have an important contribution to the spontaneous polarization of materials, with a contribution rate over 50%. The presence of hydrogen atoms in the substituting groups (MDABCO, ODABCO) enhances the hydrogen bond interaction between the organic cations and <inline-formula><tex-math id="Z-20240616143151">\begin{document}${\rm PF}_6^- $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20240385_Z-20240616143151.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20240385_Z-20240616143151.png"/></alternatives></inline-formula> and increases the displacement of the organic cation, resulting in an increase in the contribution of the polarization of the organic cation to the total polarization. In addition, we observe large piezoelectric strain components, the calculated value of <i>d</i><sub>33</sub> is 36.5 pC/N for CNDABCO-NH<sub>4</sub>-(PF<sub>6</sub>)<sub>3</sub>, 32.3 pC/N for SHNDABCO-NH<sub>4</sub>-(PF<sub>6</sub>)<sub>3</sub>, which is larger than the known value of <i>d</i><sub>33</sub> of MDABCO-NH<sub>4</sub>-I<sub>3</sub>(14pC/N). The calculated value of <i>d</i><sub>14</sub> is 57.5 pC/N for ODABCO-NH<sub>4</sub>-(PF<sub>6</sub>)<sub>3</sub>, 27.5 pC/N for NODABCO-NH<sub>4</sub>-(PF<sub>6</sub>)<sub>3</sub>. These components are at a high level among known organic perovskite materials and comparable to many known inorganic crystals. The large value of <i>d</i><sub>14</sub> is found to be closely related to the large value of elastic compliance tensor <i>s</i><sub>44</sub>. The analysis of Young’s modulus and bulk’s modulus shows that these organic perovskite materials have good ductility. These results indicate that these organic materials are excellent candidates for future environmentally friendly piezoelectric materials.

Spin texture evolution of Rashba splitting under pressure: a case study of inorganic nitride perovskite crystals

Spin–orbit coupling (SOC) effects in non-centrosymmetric systems lead to a uniform spin configuration in momentum space known as persistent spin texture (PST).

Synchronously improved luminescence efficiency and thermal stability of organic–inorganic chloride single crystals through doping of Sb3+

Synchronously improved luminescence efficiency and thermal stability of (CH3)4NMnCl3:Sb3+ crystals through doping of Sb3+ exhibits potential applications in white LEDs.

Knowledge distillation of neural network potential for molecular crystals.

Organic molecular crystals exhibit various functions due to their diverse molecular structures and arrangements. Computational approaches are necessary to explore novel molecular crystals from the material space, but quantum chemical calculations are costly and time-consuming. Neural network potentials (NNPs), trained on vast amounts of data, have recently gained attention for their ability to perform energy calculations with accuracy comparable to quantum chemical methods at high speed. However, NNPs trained on datasets primarily consisting of inorganic crystals, such as the Materials Project, may introduce bias when applied to organic molecular crystals. This study investigates the strategies to improve the accuracy of a pre-trained NNP for organic molecular crystals by distilling knowledge from a teacher model. The most effective knowledge transfer was achieved when fine-tuning using only soft targets, i.e., the teacher model's inference values. As the ratio of hard target loss increased, the efficiency of knowledge transfer decreased, leading to overfitting. As a proof of concept, the NNP created through knowledge distillation was used to predict elastic properties, resulting in improved accuracy compared to the pre-trained model.

Predicting synthesis recipes of inorganic crystal materials using elementwise template formulation.

While advances in computational techniques have accelerated virtual materials design, the actual synthesis of predicted candidate materials is still an expensive and slow process. While a few initial studies attempted to predict the synthesis routes for inorganic crystals, the existing models do not yield the priority of predictions and could produce thermodynamically unrealistic precursor chemicals. Here, we propose an element-wise graph neural network to predict inorganic synthesis recipes. The trained model outperforms the popularity-based statistical baseline model for the top-k exact match accuracy test, showing the validity of our approach for inorganic solid-state synthesis. We further validate our model by the publication-year-split test, where the model trained based on the materials data until the year 2016 is shown to successfully predict synthetic precursors for the materials synthesized after 2016. The high correlation between the probability score and prediction accuracy suggests that the probability score can be interpreted as a measure of confidence levels, which can offer the priority of the predictions.

Interstitial Oxygen Modulating Reversible Upconversion Luminescence

AbstractReversible upconversion luminescence (RUCL) through defect engineering holds great promise for various applications, including photoswitches, information recording, and storage devices. However, the reversible photoluminescence in inorganic crystals is rarely reported. Crucially, the underlying mechanism of reversible luminescence remains unclear, which challenges the design of high‐performance reversible luminescence inorganic materials. Herein, an anomalous RUCL in a class of β‐Ba2ScAlO5:Yb3+/RE3+ (RE = Er, Ho, Tm, Tb, Sm, or Eu) phosphors is reported. By alternating annealing environments (air or hydrogen), a robust and repeatable cycle of luminescence and quenching is observed. The first‐principles calculations reveal that porous β‐Ba2ScAlO5:Yb3+/RE3+ can host oxygen interstitials (during annealing in air) with a low formation energy. The interstitial oxygen state, close to the Yb 4f state, leads to luminescence quenching. Removal of oxygen interstitials (during annealing in hydrogen) can restore the luminescence by initiating radiative energy transfer. Experimentally, the existence of interstitial oxygen is confirmed with neutron diffraction technology. It is worth noting that the strong chemical bonds in crystals make adding and removing anion vacancies challenging, unlike the more “free” interstitials. The findings offer new insights into manipulating upconversion luminescence in inorganic crystals by defect engineering and provide motivation for future research in this field.

Modelling the flux decline induced by gypsum scaling in direct contact membrane distillation

Scaling has been a major technical challenge in the membrane distillation (MD) process, hindering the broader application of MD processes. Despite the increasing number of studies on MD scaling, there are limited prediction tools to describe the scaling process and help make informed decisions about the experimental conditions to prevent scaling and its irreversible damage. In this paper, a semi-analytical model was developed based on the classical nucleation theory and crystal growth to model the membrane area reduction caused by the deposition of inorganic salt crystals on the membrane surface, which is equivalent to the decrease in permeate flux resulting from scaling. The model was developed using calcium sulphate, a model scalant. The model was validated and verified with available literature data, and it has been proved that the model has the capability to produce reasonable predictions on the onset of flux decline and the declining rate with respect to the experimental data with the coefficient of determination (R2) ranging from 0.74 to 0.96. The sensitivity analysis was applied on the model, which revealed that flux decline would happen earlier in the case of higher feed temperature, higher feed velocity, and higher initial feed concentration.

CsSn2(HPO3)2I: The first inorganic metal phosphite iodide as a promising birefringent material exhibits a large birefringence with ideally layered framework

The first inorganic metal phosphite iodide, CsSn2(HPO3)2I, was successfully synthesized. It represents the first phosphite tin halide and features a [Sn(HPO3)]ꝏ layer framework structure built by the SnO3 pyramid and HPO32− groups. Attractively, it shows the most giant experimental birefringence (Δn = 0.200@0.546 μm) among reported inorganic metal phosphite birefringent crystals. This work proves that the reasonable utilization of metal cations with lone pair electrons is an effective strategy for developing excellent birefringent materials.