Decay Mechanism Research Articles

Coupling diffusion and finite deformation in phase transformation materials

We present a multiscale theoretical framework to investigate the interplay between diffusion and finite lattice deformation in phase transformation materials. In this framework, we use the Cauchy–Born Rule and the Principle of Virtual Power to derive a thermodynamically consistent theory coupling the diffusion of a guest species (Cahn–Hilliard type) with the finite deformation of host lattices (nonlinear gradient elasticity). We adapt this theory to intercalation materials – specifically Li1−2Mn2O4 – to investigate the delicate interplay between Li-diffusion and the cubic-to-tetragonal deformation of lattices. Our computations reveal fundamental insights into the microstructural evolution pathways under dynamic discharge conditions, and provide quantitative insights into the nucleation and growth of twinned microstructures during intercalation. Additionally, our results identify regions of stress concentrations (e.g., at phase boundaries, particle surfaces) that arise from lattice misfit and accumulate in the electrode with repeated cycling. These findings suggest a potential mechanism for structural decay in Li2Mn2O4. More generally, we establish a theoretical framework that can be used to investigate microstructural evolution pathways, across multiple length scales, in first-order phase transformation materials.

Two rare autosomal recessive neurological disorders identified by combined genetic approaches in a single consanguineous family with multiple offspring.

Neurodevelopmental disorders (NDDs) refer to a broad range of diseases including developmental delay, intellectual disability, epilepsy, autism spectrum disorders, and attention-deficit/hyperactivity disorder caused by dysfunctions in tightly controlled brain development. The genetic backgrounds of NDDs are quite heterogeneous; to date, recessive or dominant variations in numerous genes have been implicated. Herein, we present a large consanguineous family from Turkiye, who has been suffering from NDDs with two distinct clinical presentations. Combined in-depth genetic approaches led us to identify a homozygous frameshift variant in NALCN related to NDD and expansion of dodecamer repeat in CSTB related to Unverricht-Lundborg disease (ULD). Additionally, we sought to functionally analyze the NALCN variant in terms of mRNA expression level and current alteration. We have both detected a decrease in the level of premature stop codon-bearing mRNA possibly through nonsense-mediated mRNA decay mechanism and also an increased current in patch-clamp recordings for the expressed truncated protein. In conclusion, increased consanguinity may lead to the revealing of distinct rare neurogenetic diseases in a single family. Exome sequencing is generally considered the first-tier diagnostic test in individuals with NDD. Yet we underline the fact that customized approaches other than exome sequencing may be used as in the case of ULD to aid diagnosis and better genetic counseling.

Study of Decay Mechanisms and Rules of Recycled Asphalt Pavement via a Full-Scale Experiment

Under the influence of long-term vehicle loads and large attenuation degrees, asphalt pavement performance gradually decreases, which leads to failure in fulfilling the appropriate requirements and, in turn, may affect driving safety. The purpose of this paper was to study the attenuation mechanism and rule of styrene–butadiene–styrene (SBS)-modified recycled asphalt pavement, so as to determine the applicable position and rational utilization of recycled asphalt mixture. To achieve this goal, two structures were designed, and full-scale experiments were carried out. The performance of the field test road based on accelerated loading testing (ALT) was analyzed through field monitoring data. The fatigue characteristics of stone matrix asphalt-13 (SMA-13) and asphalt concrete-20 (AC-20) mixtures before and after accelerated loading were studied via the trabecular bending fatigue test and dynamic modulus test. The microscopic components in the asphalt mixtures were determined via thin-layer chromatography on chromarods with flame ionization detection (TLC-FID). The results showed that the fatigue properties of recycled asphalt mixture can meet the requirements of ordinary asphalt mixtures and meet the technical standards of asphalt pavement design. With the increase in loading times, the British pendulum number (BPN) value of the two structures tended to be stable, and the BPN of Plan 2 was six less than that of Plan 1. Under the same test conditions, the fatigue life sequence of the recycled asphalt mixture under different loading frequencies was 20 Hz > 10 Hz > 5 Hz. The contents of four components in the reclaimed asphalt mixture were similar to those in the ordinary asphalt mixture. The light component of the reclaimed asphalt mixture of SMA-13 was reduced by 11.69%, and the light component of the ordinary asphalt mixture of SMA-13 was reduced by 15.29% through the full-scale test. In summary, recycled asphalt mixture should not be applied to the upper layer of pavement but can be rationalized in the middle layer and the bottom layer of pavement.

Anomalous staged hot-electron acceleration by two-plasmon decay instability in magnetized plasmas.

We present a staged hot-electron acceleration mechanism of the two-plasmon decay (TPD) instability in the transverse magnetic field under the parameters relevant to inertial confinement fusion experiments. After being accelerated by the forward electron plasma wave (FEPW) of TPD, the hot-electrons can be anomalously accelerated again by the backward electron plasma wave (BEPW) of TPD and then obtain higher energy. Moreover, the surfatron acceleration mechanism of TPD in the magnetic field is also confirmed, the electrons trapped by the TPD daughter EPWs are accelerated in the direction along the wave front. Interestingly, the velocity of electrons accelerated by surfing from the FEPW is quite easily close to the BEPW phase velocity, which markedly enhances the efficiency of the staged acceleration. The coexistence of these two acceleration mechanisms leads to a significant increase of energetic electrons generated by TPD in the magnetic field. Meanwhile the EPWs are dissipated, TPD instability is effectively suppressed, and the laser transmission increases.

Spectral Heterogeneity of Phenol Blue in Protic Solvents Revealed by Ultrafast Nonradiative Decay Dynamics

AbstractPhenol blue (PhB) is a dye that exhibits positive solvatochromism which is also nonfluorescent due to its ultrashort excited state lifetime. We have conducted femtosecond time‐resolved transient absorption (TA) spectroscopic measurements of a PhB solution using two distinct excitation wavelengths, at shorter and longer wavelength sides of the visible absorption band. The results revealed that a long‐lived heterogeneity exists in protic solvents whereas, in aprotic solvents, the system rapidly returns to the original thermal equilibrium on the ultrafast timescale. Interestingly, the lifetime of the heterogeneity is longer for methanol (MeOH) compared to ethanol (EtOH) solution suggesting stronger interaction between PhB and MeOH. Additionally, since the excited state lifetime of PhB was still in the sub‐picosecond domain even in a polymer matrix, we suggest a nonradiative decay mechanism through high‐frequency vibrational modes without involving large structural reconfiguration such as twisting of the benzoquinone (BzQ) moiety.

Study on the thermal decay mechanism of basalt fiber reinforced resin based friction materials

PurposeResin-based friction materials are the most widely used key materials in industry for braking and transmission. However, the friction coefficient of resin-based friction materials significantly decreases at temperatures above 300°C, which reduces their friction performance.Design/methodology/approachThis study combines elevated-temperature mechanical experiments with friction and wear experiments to explain the thermal degradation resistance performance and temperature recovery performance of resin-based friction materials. It also investigates the influence of friction material strength and worn morphology on the friction coefficient of materials at elevated temperature.FindingsThe experimental results show that the increase in friction coefficient of friction materials below 300°C is mainly due to the increase in worn morphology characterization parameters, and the thermal degradation phenomenon above 300°C is mainly due to the decrease of shear strength of friction film. Basalt fiber can significantly improve the thermal degradation resistance of friction materials. The friction coefficient of basalt fiber-reinforced specimens after thermal degradation reaches 0.421–0.443, which is 19–25% higher than the original. The thermal decay rate is 9.03–11.0%, which is 7.9–9.87% lower than the original. Moreover, the friction coefficient has good cooling recovery performance.Originality/valueRevealed the thermal degradation mechanism of resin-based friction materials, verified that basalt fibers can improve the thermal degradation resistance of friction materials and provided reference for the development of new friction materials.

Four different gene-related cone-rod dystrophy: clinical and genetic findings in six Chinese families with diverse modes of inheritance.

Purpose: To investigate pathogenic variants in six families with cone-rod dystrophy (CORD) presenting various inheritance patterns by using whole-exome sequencing (WES) and analyzing phenotypic features. Methods: A total of six families with CORD were enrolled in Ningxia Eye Hospital for this study. The probands and their family members received comprehensive ophthalmic examinations, and DNA was abstracted from patients and family members. Whole-exome sequencing was performed on probands to screen the causative variants, and all suspected pathogenic variants were determined via Sanger sequencing. Furthermore, co-segregation analysis was performed on available family members. The pathogenicity of novel variants was predicted using in silico analysis and evaluated according to the American College of Medical Genetics and Genomics (ACMG) guidelines. Results: Of the six families, two families were assigned as X-linked recessive (XL), two families were assigned as autosomal recessive (AR), and two families were assigned as autosomal dominant (AD). Pathogenic variants were detected in CACNA1F in two X-linked recessive probands, among which family 1 had a hemizygous frameshift variant c.2201del (p.Val734Glyfs*17) and family 2 had a hemizygous missense variant c.245G>A (p.Arg82Gln). Both probands had high myopia, with fundus tessellation accompanied by abnormalities in the outer structure of the macular area. The homozygous splice variant c.2373 + 5G>T in PROM1 and the homozygous nonsense variant c.604C>T (p.Arg202Ter) in ADAM9 were detected in two autosomal recessive families of the probands. Both probands showed different degrees of atrophy in the macular area, and the lesions showed hypofluorescence changes in autofluorescence. The heterozygous variation in CRX c.682C>T (p.Gln228Ter) was detected in two autosomal dominant families. The onset age of the two probands was late, with better vision and severe macular atrophy. According to ACMG guidelines and the analysis of online in silico tools, all variations were labeled as potentially harmful or pathogenic. Conclusion: Pathogenic variants in CACNA1F, PROM1, ADAM9, and CRX genes were identified in six families affected by the diverse inheritance patterns of CORD. Furthermore, the potential impact of the nonsense-mediated decay (NMD) mechanism on the manifestation of CORD phenotypes was examined and addressed. Simultaneously, the spectrum of pathogenic variants and clinical phenotypes associated with the CORD gene was extended.

A new efficient ALignment-driven Neural Network for Mortality Prediction from Irregular Multivariate Time Series data

The irregularity of the time interval between observations in and across the stream is a key factor that leads to a drop in performance when classical machine learning or deep learning models are used for a downstream task requiring multivariate time series. Indeed, irregular multivariate time series not only increase the rate of missing values but also lead to data sparsity, which consequently makes the data almost unleverageable and/or ineffective for models. To tackle this scorching challenge, most of the pioneering approaches apply imputation or interpolation in their core, which might lead to embedding data with noise. To especially address this irregular multivariate time series issue, we introduce, in this paper, a new deep neural network model called ALignment-driven Neural Network. The innovative idea of our model is to transform the irregular multivariate time series into pseudo-aligned (or pseudo-regular) latent values. The latter are shown as a matrix, where the coefficients are the latent values of each feature at user-defined reference time points that are evenly spaced. They are obtained through a duplication process driven by an exponential decay mechanism. The obtained output is then passed to a Recurrent Neural Network model, which is undoubtedly the must-use model for regular time series data. To show that our model added value, we looked at the Intensive Care Unit mortality prediction task. In this unit, the physiological measurements used to make decisions have a problem with time irregularity. Leveraging the publicly available MIMIC-III, we compare the performance of our model to that of flagship models. In addition, we also performed extensive ablation studies to highlight the importance of specific components in our model. Interestingly enough, whenever data is collected 24 and 48 h after a patient’s admission, we outperform our pioneering competitors, i.e., +1.1% and +1.5% for the AUC score, +2.3% and +2.4% for the AUPRC score and +0.6% and +1.7% for the F1-score.

Design Strategies for Luminescent Titanocenes: Improving the Photoluminescence and Photostability of Arylethynyltitanocenes.

Complexes that undergo ligand-to-metal charge transfer (LMCT) to d0 metals are of interest as possible photocatalysts. Cp2Ti(C2Ph)2 (where C2Ph = phenylethynyl) was reported to be weakly emissive in room-temperature (RT) fluid solution from its phenylethynyl-to-Ti 3LMCT state but readily photodecomposes. Coordination of CuX between the alkyne ligands to give Cp2Ti(C2Ph)2CuX (X = Cl, Br) has been shown to significantly increase the photostability, but such complexes are not emissive in RT solution. Herein, we investigate whether inhibition of alkyne-Ti-alkyne bond compression might be responsible for the increased photostability of the CuX complexes by investigating the decomposition of a structurally constrained analogue, Cp2Ti(OBET) (OBET = o-bis(ethynyl)tolane). To investigate the mechanism of nonradiative decay from the 3LMCT states in Cp2Ti(C2Ph)2CuX, the photophysical properties were investigated both upon deuteration and upon rigidifying in a poly(methyl methacrylate) film. These investigations suggested that inhibition of structural rearrangement may play a dominant role in increasing emission lifetimes and quantum yields. The bulkier Cp*2Ti(C2Ph)2CuBr was prepared and is emissive at 693 nm in RT THF solution with a photoluminescent quantum yield of 1.3 × 10-3 (τ = 0.18 μs). Time-dependent density functional theory (TDDFT) calculations suggest that emission occurs from a 3LMCT state dominated by Cp*-to-Ti charge transfer.

Truncated DNM1 variant underlines developmental delay and epileptic encephalopathy.

Developmental and epileptic encephalopathies (DEEs) signify a group of heterogeneous neurodevelopmental disorder associated with early-onset seizures accompanied by developmental delay, hypotonia, mild to severe intellectual disability, and developmental regression. Variants in the DNM1 gene have been associated with autosomal dominant DEE type 31A and autosomal recessive DEE type 31B. In the current study, a consanguineous Pakistani family consisting of a proband (IV-2) was clinically evaluated and genetically analyzed manifesting in severe neurodevelopmental phenotypes. WES followed by Sanger sequencing was performed to identify the disease-causing variant. Furthermore, 3D protein modeling and dynamic simulation of wild-type and mutant proteins along with reverse transcriptase (RT)-based mRNA expression were checked using standard methods. Data analysis of WES revealed a novel homozygous non-sense variant (c.1402G>T; p. Glu468*) in exon 11 of the DNM1 gene that was predicted as pathogenic class I. Variants in the DNM1 gene have been associated with DEE types 31A and B. Different bioinformatics prediction tools and American College of Medical Genetics guidelines were used to verify the identified variant. Sanger sequencing was used to validate the disease-causing variant. Our approach validated the pathogenesis of the variant as a cause of heterogeneous neurodevelopmental disorders. In addition, 3D protein modeling showed that the mutant protein would lose most of the amino acids and might not perform the proper function if the surveillance non-sense-mediated decay mechanism was skipped. Molecular dynamics analysis showed varied trajectories of wild-type and mutant DNM1 proteins in terms of root mean square deviation, root mean square fluctuation and radius of gyration. Similarly, RT-qPCR revealed a substantial reduction of the DNM1 gene in the index patient. Our finding further confirms the association of homozygous, loss-of-function variants in DNM1 associated with DEE type 31B. The study expands the genotypic and phenotypic spectrum of pathogenic DNM1 variants related to DNM1-associated pathogenesis.

Multi-Scale Decay Mechanism of Emulsified Asphalt Cold Recycled Mixture Under Freeze-Thaw

The road performance decay law of EACRM under freeze-thaw cycles was studied using laboratory tests on the macroscopic scale in order to comprehensively analyze the serious performance damage mechanism of emulsified asphalt cold recycled mixture (EACRM) in cold regions during the service period. The surface cracking behavior, internal void evolution characteristics, and asphalt mortar morphology damage of EACRM under freeze-thaw cycles were studied by means of digital speckle, industrial CT, and scanning electron microscope (SEM) on the mesoscopic and microscopic scale. The results show that along with the increase in the number of freeze-thaw cycles, the road performance of EACRM decreases significantly. The surface of EACRM obviously cracks, and the width and number of main cracks increase significantly. The fatigue times of the maximum horizontal strain in the whole field gradually decrease. Air voids and the average volume of meso-void visibly increase. The microcracks of cement-emulsified asphalt mortar constantly emerge at the interface. The serious damage of the “three-dimensional network structure” is the fundamental reason for the performance decay of EACRM in cold regions. The performance damage of EACRM in cold regions is aggravated by water seeping into voids from cracks. Eventually, EACRM shows serious freeze-thaw inflicted damage.

The fitness and corrosion mechanisms of high‐strength steel in corrosive oil–water environment at high temperature

AbstractThis work investigated the mechanical decay mechanism and high‐temperature corrosion mechanism of high‐strength steel via high‐temperature mechanical experiments, and corrosion and stress corrosion cracking tests were performed in simulated working conditions where water, oil, H2S, and CO2 coexist. The results show that the tensile strength and yield strength of high‐strength steel decrease with increasing temperature; the tensile strength and yield strength at 350°C reduce 11.91% and 19.08%, respectively, compared with 25°C. Moreover, the corrosion rate of high‐strength steel gradually increased from 0.0914 mm/a at 150°C to 1.2288 mm/a at 350°C. In addition, the influence of high temperature on the corrosion mechanism was inferred through thermodynamic calculations, and the reason for the presence of Fe3O4 in the corrosion products at 350°C was analyzed. At 350°C, stress corrosion cracking was observed in high‐strength steels when the applied stress reached 90% of the yield strength. Based on the aforementioned studies, the relevant mechanisms related to the decay of mechanical properties, corrosion, and stress corrosion cracking are also proposed.

Beyond vanilla: The dissociation mechanism of vanillin in four charge states

We compare the unimolecular decay mechanism of vanillin in four charge states. The unimolecular thermal decomposition of the neutral and dissociative ionization reactions in the cation have already been addressed in synchrotron-based photoionization studies. The picture is completed here by studying the collision-induced dissociation mechanism of protonated vanillin cations and deprotonated vanillin anions in the 5–30 eV collision energy range. The mass spectrometric observations are rationalized by ab initio calculations, which reveal the mechanism and the energetics of dissociation pathways. In the positive ion mode, the aldehyde oxygen is protonated, after which CO is lost. In contrast to previous results, CO loss is found to be the sole primary fragmentation pathway of protonated vanillin. Two hydrogen migration steps to the benzene ring open sequential CH3OH and CH3 loss channels to yield C6H5O+ and C6H6O2+, respectively. The former fragment ion can continue to lose CO, associated with ring contraction and producing the cyclopentadiene cation, C5H5+. In the negative ion mode, the proton is removed from the hydroxyl group. The primary dissociation channel of deprotonated vanillin corresponds to (C)OCH3 bond breaking in the methoxy group to form C7H4O3− at m/z 136. This species goes on to produce C6H4O2− and C6H4O− anions via CO and CO2 loss, respectively, in sequential dissociation processes at higher collision energies. We compare the protonated and deprotonated vanillin fragmentation pathways with those observed in the decomposition of neutral vanillin and with the dissociation pathways of the vanillin cation. The initial decomposition step for neutral, cationic, and deprotonated vanillin is methyl loss by direct CO bond breaking, often followed by loss of CO. In contrast, protonated vanillin first loses CO after isomerization.

When wood cladding degenerates

For several decades, the mechanisms of decay of wood exposed outdoor have been scrutinized in order to ameliorate the performances of this versatile material when used for purposes such as house cladding. Performance of cladding seems to be highly depending on durability of wood, in its turn directly connected to water uptake which can vary a lot. How long a cladding can function for is particularly complicated to define also because of its paradoxical role of sacrificial and aesthetic layer. Anyhow, thanks to small reparations and maintenance, many traditional claddings are still preserved. They have been produced and maintained with local resources and show that low-processed wood can be durable in outdoor conditions. The contrast with modern approaches such as wood modification or importation of durable species, lifts the question: what durability of wood is concretely required for cladding purposes? The exhibition shows characteristics of wood weathered for up to hundreds of years, allowing to understand what impact damages can have on cladding’s performance. The samples, issued from traditional French and Scandinavian facades, illustrate how exposure level influences degradation, confirming the role of rot and revealing the one of erosion in degeneration of wood cladding. Both Alder and Pine seem to have the potential to naturally perform well as cladding for longer than it takes for the trees to regenerate. Traditions might teach us how to use local wood in a durable way if we consider biodegradation as an opportunity to build without creating wastes, rather than as a threat.

Synthesis, structural, spectral, thermal, and optical characterization of a new curcumin derivative: A promising material for NLO applications

A novel Curcumin derivative 1-(4-chlorobenzoyl)-3,5-bis((E)-3,4-dimethoxybenzylidene)piperidin-4-one (CDMBP) has been synthesized by Claisen-Schmidt condensation and Schotten-Baumann reaction methods. CDMBP single crystal was grown from acetone by slow evaporation method at ambient temperature. The crystal structure of the compound was derived by Single Crystal X-ray Diffraction studies (SCXRD). The title compound CDMBP was crystallized in a triclinic crystal system with a P ͞1 space group. NMR spectral analysis reveals the different types of carbon and proton in the molecular structure of the title compound. The modes of vibrations of different chemical groups were identified using FT-Raman and Fourier Transform Infrared spectral analysis (FTIR). Utilizing the UV–Vis spectrum, the cutoff wavelength and linear optical constants such as the band gap, extinction coefficient, and refractive index were calculated. The Photoluminescence spectrum (PL) has been studied and it shows a high-intensity peak at 504 nm and belongs to the green emission radiation region. Fluorescence profiling of the compound was done to get an outline of the emission features of the excited states with the emission decay mechanisms using Lifetime measurements. The third-order nonlinear optical property (NLO) of CDMBP was investigated in detail using a Z-scan technique with a He–Ne laser at 632.8 nm as a laser source. The nonlinear optical susceptibility (χ3), absorption coefficient (β), and refractive index (n) were calculated using transmittance data. The thermal stability of the grown crystal was investigated from the Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA).

Effect of ultraviolet aging of backsheet on electrical performance of silicon photovoltaic module

Photovoltaic (PV) backsheets protect solar cells from corrosion, moisture intrusion, and environmental pollution, and they also reflect light to be reabsorbed by solar cells. Previous studies have confirmed that PV backsheet materials can affect the performance of PV modules. In this study, the performance of the backsheet under a single ultraviolet (UV) aging condition and its influence on the electrical performance of the PV module were explored so as to establish the relationship between backsheet aging and PV module performance. The results of this study show that UV irradiation is the main factor leading to the aging and cracking of backsheets. When the backsheet was exposed to a UV dose of 60 kWh/m2, the elongation at break of the backsheet was reduced by 97.04%, the tensile strength was reduced by 60.10%, the reflectivity of the backsheet was reduced by 8.36%, and the power and short-circuit current of the PV module decreased by 3.69% and 3.96%, respectively. The primary cause for the decline in PV module power was determined to be the reduction in backsheet reflectivity, which diminished the available light that could undergo re-reflection onto the solar cell, thereby resulting in a reduction of the short-circuit current. These findings provide valuable insights into the changes in the physicochemical properties of UV-aged backsheets and their power decay mechanism in PV modules. The results establish an invaluable link between the testable characteristics of backsheet aging and PV module performance.

Electromagnetic time-like form factors

We present the calculation of charged pion and kaon electromagnetic form factors in the time-like regime using Schwinger-Dyson equations and the Poincare covariant Bethe-Salpeter equations within an SU(2) isospin symmetric limit. To accurately represent the behavior of a time-like photon, we have incorporated non-valence contributions into the system of equations, enabling the decays ρ → ππ and φ → KK. The inclusion of these decay mechanisms is essential for capturing the expected behavior of the electromagnetic pion and kaon form factors. Our results for the form factors reasonably reproduce the experimental data for a time-like photon.

Electrochromic Materials: Scope for the Cyclic Decay Mechanisms and Performance Stability Optimization Strategies

AbstractElectrochromic materials (ECMs) have important potential applications in the field of intelligent optoelectronic displays. However, ECMs and its devices cannot be truly applied on a large scale until the problem of their long‐period performance degradation is really solved. This paper focuses on summarizing the attenuation mechanism of common ECMs, which is mainly divided into three types: structural damage, irreversible reaction and ion capture, and summarizes four optimization strategies for the cyclic stability of electrochromic materials at the present stage: doping is used to change the internal structure of the material in order to achieve the purpose of improving the cyclic stability; composite means to allow a variety of materials to interact with each other in order to get the original material has no excellent performance; improve the cyclic stability of electrochromic materials by the special characteristics of nanostructures; and enhance the performance by optimizing the preparation process and regulating the parameters in the preparation process. Finally, the paper discusses the potential for optimizing the long‐term stability of ECMs in the future, based on the above research.This article is protected by copyright. All rights reserved.

Insights into the Luminescence Quantum Yields of Cyclometalated Iridium(III) Complexes: A Density Functional Theory and Machine Learning Approach.

Cyclometalated iridium(III) complexes have been used in various optical materials, including organic light-emitting diodes (OLEDs) and photocatalysts, and a deeper understanding and prediction of their luminescence quantum yields (LQYs) greatly aid in accelerating material design. In this study, we integrated density functional theory (DFT) calculations with machine learning (ML) techniques to extract factors controlling LQY. Although a substantial data set of Ir(III) complexes and their LQYs is indispensable for constructing accurate ML models to predict LQYs, generating this type of data set is challenging due to the complexities associated with ab initio calculations of LQYs. To address this issue, we investigated the nonradiative decay process of nine Ir(III) complexes emitting blue to green, each exhibiting varying experimental LQYs, by using DFT calculations. For all nine complexes, the quenching process was induced by the rotation of the single bond in one of the ligands, which converted the six-coordinate structure to the five-coordinate structure. Since the decay mechanism was common for the nine Ir(III) complexes, parameters correlated with LQYs could be used as objective variables instead of LQYs. Based on this idea, we collected a data set featuring Ir(III) complexes and the energy differences between their six- and five-coordinate triplet structures, which correlated with LQYs. We also constructed ML models using the calculated LQYs as the objective variables with the parameters from the ground-state calculations as explanatory variables. The analyses of the constructed model revealed that the LUMO energy of the ligand made the most significant negative contribution to LQY. This suggests that the potential energy surface of the metal-to-ligand charge transfer (MLCT) excited state, which stabilizes the six-coordinate structure, is reduced by decreasing the energy of the unoccupied orbitals.

Understanding Capacity Fade in Organic Redox-Flow Batteries by Combining Spectroscopy with Statistical Inference Techniques

Aqueous-soluble organic and organometallic redox-active molecules show considerable promise as redox-flow battery (RFB) reactants because their costs at scale are projected to be low. However, most aqueous organic RFB undergo rapid degradation resulting in high rates of capacity fade. Considerable research has been devoted towards discovering chemically stable charge carriers for RFBs. However, the decomposition mechanisms of underperforming chemistries during flow cell cycling are often poorly understood, and in some instances, competing or incompatible hypotheses about the relationship between reactant decay and capacity fade have often been proposed.In this talk, we will demonstrate that combining spectroscopic and statistical inference techniques can be used to shed light on relationship between RFB reactant degradation and capacity fade. Specifically, we employ in operando ultraviolet-visible spectrophotometry along with Bayesian inference, Bayesian model selection, and multivariate curve regression in order to quantify the relative probabilities of different decay mechanisms given the data at hand, and to estimate rate constants for specific reactions within the most probable decay scheme. In principle, rate constants thus obtained can be fed into a zero-dimensional electrochemical flow cell model, recently developed by our group, that can simulate capacity fade given a reactant decay mechanism, associated rates, and the cycling protocol. This work has the potential to shed light on the relationship between capacity fade and reactant decay in various organic RFB chemistries, and to enable prediction of the lifetimes of commercial-scale RFBs.