Philipp C Schmid, Samuel J P Marlton, Weslley G D P Silva, Thomas Salomon, János Sarka, Sven Thorwirth, Oskar Asvany, Stephan Schlemmer
Rovibrational spectra of the open-shell linear cations HCN+ (X̃2Π) and HNC+ (X̃2Σ+) are measured with leak-out spectroscopy in cryogenic 22-pole ion traps. The fundamental ν1 C-H stretching vibration of HCN+ is found at 3056.3412(1) cm-1 and the lower energy Renner-Teller (RT) component (Σ) of the ν1 + ν2 combination band is found at 3340.8480(2) cm-1. The resulting effective RT vibrational frequency of ≈300 cm-1 inferred from the comparison of these two bands indicates a large Renner-Teller splitting for HCN+. For HNC+, the ν1 N-H stretching vibration is found at 3407.9136(4) cm-1, much higher than expected from previous matrix work. Thanks to the rotational resolution of these infrared measurements, spectroscopic constants for the electronic fine-structure, molecular rotation, centrifugal distortion, Λ-doubling and spin-rotation interaction have been determined for the vibrational ground and excited states with high confidence. The infrared spectrum of HCN+ is rather rich and contains more bands including, e.g., the electronic à ← X̃ transition. The analysis of this band and the pure rotational spectrum of HCN+ will be the subject of further publications.
{"title":"High-resolution spectroscopy of [H,C,N]<sup>+</sup>: I. Rotationally resolved vibrational bands of HCN<sup>+</sup> and HNC<sup />.","authors":"Philipp C Schmid, Samuel J P Marlton, Weslley G D P Silva, Thomas Salomon, János Sarka, Sven Thorwirth, Oskar Asvany, Stephan Schlemmer","doi":"10.1039/d5cp04201a","DOIUrl":"10.1039/d5cp04201a","url":null,"abstract":"<p><p>Rovibrational spectra of the open-shell linear cations HCN<sup>+</sup> (X̃<sup>2</sup>Π) and HNC<sup>+</sup> (X̃<sup>2</sup>Σ<sup>+</sup>) are measured with leak-out spectroscopy in cryogenic 22-pole ion traps. The fundamental <i>ν</i><sub>1</sub> C-H stretching vibration of HCN<sup>+</sup> is found at 3056.3412(1) cm<sup>-1</sup> and the lower energy Renner-Teller (RT) component (Σ) of the <i>ν</i><sub>1</sub> + <i>ν</i><sub>2</sub> combination band is found at 3340.8480(2) cm<sup>-1</sup>. The resulting effective RT vibrational frequency of ≈300 cm<sup>-1</sup> inferred from the comparison of these two bands indicates a large Renner-Teller splitting for HCN<sup>+</sup>. For HNC<sup>+</sup>, the <i>ν</i><sub>1</sub> N-H stretching vibration is found at 3407.9136(4) cm<sup>-1</sup>, much higher than expected from previous matrix work. Thanks to the rotational resolution of these infrared measurements, spectroscopic constants for the electronic fine-structure, molecular rotation, centrifugal distortion, <i>Λ</i>-doubling and spin-rotation interaction have been determined for the vibrational ground and excited states with high confidence. The infrared spectrum of HCN<sup>+</sup> is rather rich and contains more bands including, <i>e.g.</i>, the electronic à ← X̃ transition. The analysis of this band and the pure rotational spectrum of HCN<sup>+</sup> will be the subject of further publications.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12851410/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146091604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Joshua H. Marks, Jia Wang, Ryan C. Fortenberry, Ralf I. Kaiser
The simplest sugar — glyceraldehyde (HOCH2CH(OH)CHO) — represents a central molecule in the biochemistry of all lifeforms (glycolysis/gluconeogenesis). Linking photosynthesis and carbon fixation to sugar metabolism is fundamental to the liberation of energy from sugars and is the point at which glycolysis becomes exothermic — the pay-off phase. By exploiting isomer-selective photoionization reflectron time-of-flight mass spectrometry, glyceraldehyde and its energetic enol isomer 1,2,3-propenetriol (HOCH2C(OH)CHOH) are identified in situ during space-simulation experiments as reaction products of radicals formed in ethylene glycol (HOCH2CH2OH) and carbon monoxide (CO) interstellar model ices exposed to proxies for galactic cosmic rays. Isotopic substitution demonstrates the mechanism of sugar formation from molecules abundant in the interstellar medium. The stability of the carbon-centered radical intermediates formyl (HĊO) and 1,2-dihydroxyethyl (HOCH2ĊHOH) imply that reactions of carbon monoxide and methanol derivatives like ethylene glycol represent a facile, highly active mechanism of sugar production within ice coated interstellar grains in deep space.
{"title":"An Efficient Route to Glyceraldehyde (HOCH2CH(OH)CHO) — The Simplest Aldose — via Reactions of Carbon-Centered Radicals in Deep Space","authors":"Joshua H. Marks, Jia Wang, Ryan C. Fortenberry, Ralf I. Kaiser","doi":"10.1039/d5cp04397b","DOIUrl":"https://doi.org/10.1039/d5cp04397b","url":null,"abstract":"The simplest sugar — glyceraldehyde (HOCH<small><sub>2</sub></small>CH(OH)CHO) — represents a central molecule in the biochemistry of all lifeforms (glycolysis/gluconeogenesis). Linking photosynthesis and carbon fixation to sugar metabolism is fundamental to the liberation of energy from sugars and is the point at which glycolysis becomes exothermic — the pay-off phase. By exploiting isomer-selective photoionization reflectron time-of-flight mass spectrometry, glyceraldehyde and its energetic enol isomer 1,2,3-propenetriol (HOCH<small><sub>2</sub></small>C(OH)CHOH) are identified in situ during space-simulation experiments as reaction products of radicals formed in ethylene glycol (HOCH<small><sub>2</sub></small>CH<small><sub>2</sub></small>OH) and carbon monoxide (CO) interstellar model ices exposed to proxies for galactic cosmic rays. Isotopic substitution demonstrates the mechanism of sugar formation from molecules abundant in the interstellar medium. The stability of the carbon-centered radical intermediates formyl (HĊO) and 1,2-dihydroxyethyl (HOCH<small><sub>2</sub></small>ĊHOH) imply that reactions of carbon monoxide and methanol derivatives like ethylene glycol represent a facile, highly active mechanism of sugar production within ice coated interstellar grains in deep space.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"72 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Suryasunil Rath, Priyabrata Das, Pulak M Pandey, Satyananda Kar
Microwave atmospheric pressure plasma jets (MW-APPJs) exhibit significant potential for diverse applications, i.e., hydrogen production, CO2 dissociation, water treatment, material processing and waste treatment due to their stable operation at atmospheric pressure and generation of highly tunable reactive species. For effective utilization of MW-APPJs, a detailed understanding of the operational conditions that influence plasma parameters is essential. The present work proposes an uncertainty-aware, multi-output, interpretable supervised machine learning (ML) framework to predict eight plasma parameters, viz electron excitation temperature (Texc), electron number density (ne), four reactive species (OH, N2, Hα and O), gas temperature (Tg), and plume length. A dataset comprising 441 experimental runs was generated by varying input powers (700-1000 W), sliding short positions (0.95-1.05 λg/2) and argon flow rate (5-15 lpm). Six regression models namely k-nearest neighbours (KNN), extra trees (ET), random forest (RF), artificial neural networks (ANN), gradient boosting (GB), and extreme gradient boosting (XGB) were optimized using Bayesian hyperparameter tuning and evaluated using both accuracy and reliability metrics. While XGB achieved competitive pointwise accuracy, the optimized GB model emerged as the most balanced performer when predictive accuracy, calibration behaviour, and uncertainty reliability were jointly considered. On a held-out test set, the GB model achieved mean absolute percentage errors below 3% and R² values exceeding 0.97 across all plasma parameters. Bootstrap-based uncertainty quantification demonstrated near-nominal 90% prediction interval coverage with comparatively narrow uncertainty bounds, and calibration analysis confirmed statistically consistent uncertainty estimates. Experimental validation using 30 independent plasma operating conditions, separated into interpolated and extrapolated regimes, further confirmed robust generalization, with increased epistemic uncertainty appropriately accompanying extrapolative predictions. SHapley Additive exPlanations (SHAP) based interpretability analysis identified microwave power as the dominant controlling feature for most plasma parameters, while gas flow rate governed the intensity of OH emission. Overall, this uncertainty-aware ML framework provides a reliable foundation for data-driven plasma diagnostics and future optimization of MW-APPJ-based processes.
{"title":"Uncertainty-Aware Machine Learning-Based Prediction of Plasma Parameters in a Microwave Atmospheric Pressure Plasma Jet","authors":"Suryasunil Rath, Priyabrata Das, Pulak M Pandey, Satyananda Kar","doi":"10.1039/d5cp04364f","DOIUrl":"https://doi.org/10.1039/d5cp04364f","url":null,"abstract":"Microwave atmospheric pressure plasma jets (MW-APPJs) exhibit significant potential for diverse applications, i.e., hydrogen production, CO2 dissociation, water treatment, material processing and waste treatment due to their stable operation at atmospheric pressure and generation of highly tunable reactive species. For effective utilization of MW-APPJs, a detailed understanding of the operational conditions that influence plasma parameters is essential. The present work proposes an uncertainty-aware, multi-output, interpretable supervised machine learning (ML) framework to predict eight plasma parameters, viz electron excitation temperature (Texc), electron number density (ne), four reactive species (OH, N2, Hα and O), gas temperature (Tg), and plume length. A dataset comprising 441 experimental runs was generated by varying input powers (700-1000 W), sliding short positions (0.95-1.05 λg/2) and argon flow rate (5-15 lpm). Six regression models namely k-nearest neighbours (KNN), extra trees (ET), random forest (RF), artificial neural networks (ANN), gradient boosting (GB), and extreme gradient boosting (XGB) were optimized using Bayesian hyperparameter tuning and evaluated using both accuracy and reliability metrics. While XGB achieved competitive pointwise accuracy, the optimized GB model emerged as the most balanced performer when predictive accuracy, calibration behaviour, and uncertainty reliability were jointly considered. On a held-out test set, the GB model achieved mean absolute percentage errors below 3% and R² values exceeding 0.97 across all plasma parameters. Bootstrap-based uncertainty quantification demonstrated near-nominal 90% prediction interval coverage with comparatively narrow uncertainty bounds, and calibration analysis confirmed statistically consistent uncertainty estimates. Experimental validation using 30 independent plasma operating conditions, separated into interpolated and extrapolated regimes, further confirmed robust generalization, with increased epistemic uncertainty appropriately accompanying extrapolative predictions. SHapley Additive exPlanations (SHAP) based interpretability analysis identified microwave power as the dominant controlling feature for most plasma parameters, while gas flow rate governed the intensity of OH emission. Overall, this uncertainty-aware ML framework provides a reliable foundation for data-driven plasma diagnostics and future optimization of MW-APPJ-based processes.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"206 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Maximilian Litterst, Manjunath Balagopalan, Ramon Jannasch, Elin D Sødahl, Seyedmojtaba Seyedraoufi, Carl H. Gorbitz, Kristian Berland, Ola Nilsen, Martijn Kemerink
Compared to inorganic ferroelectrics, the breadth of polarization switching mechanisms in organic ferroelectrics is very broad and far from fully characterized or understood. Here, we experimentally investigate the absence or presence of ferroelectric properties in a selection of organic materials that have been identified by a data mining approach using heuristic measures to identify stretchability, aiming to assess the practical potential of this approach. From a set of 66 candidate materials, 4 were selected for detailed analysis. These were investigated structurally using powder X-ray diffraction and electrically, using capacitance-voltage spectroscopy and polarization hysteresis measurements. Despite large differences in stability and background conductivity, all compounds exhibited ferroelectric behavior at room temperature, with relatively large polarization values. Specifically, the ferroelectric properties of one material show a strong dependency on the ambient humidity, whereas another showed a strong coupling between background conductivity and ferroelectric switching. These effects are not yet fully understood and lie beyond the scope of this study. Of the remaining two compounds, one was found to be unstable at room temperature whereas the other displayed multiple polymorphs, complicating reproducibility and limiting their practical potential. Overall, these results confirm the relevance of the data mining prediction scheme and suggest that a significant fraction of the identified but so far untested materials may also be ferroelectric.
{"title":"Experimentally confirmed ferroelectricity in organic compounds identified by database mining","authors":"Maximilian Litterst, Manjunath Balagopalan, Ramon Jannasch, Elin D Sødahl, Seyedmojtaba Seyedraoufi, Carl H. Gorbitz, Kristian Berland, Ola Nilsen, Martijn Kemerink","doi":"10.1039/d5cp03009a","DOIUrl":"https://doi.org/10.1039/d5cp03009a","url":null,"abstract":"Compared to inorganic ferroelectrics, the breadth of polarization switching mechanisms in organic ferroelectrics is very broad and far from fully characterized or understood. Here, we experimentally investigate the absence or presence of ferroelectric properties in a selection of organic materials that have been identified by a data mining approach using heuristic measures to identify stretchability, aiming to assess the practical potential of this approach. From a set of 66 candidate materials, 4 were selected for detailed analysis. These were investigated structurally using powder X-ray diffraction and electrically, using capacitance-voltage spectroscopy and polarization hysteresis measurements. Despite large differences in stability and background conductivity, all compounds exhibited ferroelectric behavior at room temperature, with relatively large polarization values. Specifically, the ferroelectric properties of one material show a strong dependency on the ambient humidity, whereas another showed a strong coupling between background conductivity and ferroelectric switching. These effects are not yet fully understood and lie beyond the scope of this study. Of the remaining two compounds, one was found to be unstable at room temperature whereas the other displayed multiple polymorphs, complicating reproducibility and limiting their practical potential. Overall, these results confirm the relevance of the data mining prediction scheme and suggest that a significant fraction of the identified but so far untested materials may also be ferroelectric.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"292 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jing-Jing He, Jun-Yi Gu, Qin-Yue Cao, Ling-Xiao Liu, Min Hua, Jia-Ren Yuan, Yan-Dong Guo, Xiao-Hong Yan
Two-dimensional multiferroic materials, which exhibit both ferroelectricity and ferromagnetism, have drawn significant interest due to their capability to control electronic and magnetic properties via polarization switching. In this work, we designed a multiferroic van der Waals heterostructure (vdWH) made of 2D ferromagnetic Cr2Cl3S3 and ferroelectric Ga2O3, and examined its structural, electronic, and magnetic properties through first-principles calculations. The results demonstrate that by manipulating the polarization state of Ga2O3, the Cr2Cl3S3(Cl)/Ga2O3 vdWH can reversibly switch between semiconductor and half-metal, whereas the Cr2Cl3S3(S)/Ga2O3 vdWH can transition reversibly between semiconductor and metal. These reversible transitions are attributed to the shift in band alignment induced by interlayer charge transfer. Notably, as the spintronic properties of the Cr2Cl3S3(S)/Ga2O3 vdWH change, its easy magnetization axis also switches from in-plane to out-of-plane. The switchable electrical control of heterostructures by ferroelectric Ga2O3 is nonvolatile. These findings are important for understanding ferroelectric control of spintronics and electromagnetic coupling and provide a potential route for developing multiferroic memory devices.
{"title":"Electronic and magnetic properties modulated by nonvolatile switching in the multiferroic Cr<sub>2</sub>Cl<sub>3</sub>S<sub>3</sub>/Ga<sub>2</sub>O<sub>3</sub> van der Waals heterostructure.","authors":"Jing-Jing He, Jun-Yi Gu, Qin-Yue Cao, Ling-Xiao Liu, Min Hua, Jia-Ren Yuan, Yan-Dong Guo, Xiao-Hong Yan","doi":"10.1039/d5cp03967c","DOIUrl":"https://doi.org/10.1039/d5cp03967c","url":null,"abstract":"<p><p>Two-dimensional multiferroic materials, which exhibit both ferroelectricity and ferromagnetism, have drawn significant interest due to their capability to control electronic and magnetic properties <i>via</i> polarization switching. In this work, we designed a multiferroic van der Waals heterostructure (vdWH) made of 2D ferromagnetic Cr<sub>2</sub>Cl<sub>3</sub>S<sub>3</sub> and ferroelectric Ga<sub>2</sub>O<sub>3</sub>, and examined its structural, electronic, and magnetic properties through first-principles calculations. The results demonstrate that by manipulating the polarization state of Ga<sub>2</sub>O<sub>3</sub>, the Cr<sub>2</sub>Cl<sub>3</sub>S<sub>3</sub>(Cl)/Ga<sub>2</sub>O<sub>3</sub> vdWH can reversibly switch between semiconductor and half-metal, whereas the Cr<sub>2</sub>Cl<sub>3</sub>S<sub>3</sub>(S)/Ga<sub>2</sub>O<sub>3</sub> vdWH can transition reversibly between semiconductor and metal. These reversible transitions are attributed to the shift in band alignment induced by interlayer charge transfer. Notably, as the spintronic properties of the Cr<sub>2</sub>Cl<sub>3</sub>S<sub>3</sub>(S)/Ga<sub>2</sub>O<sub>3</sub> vdWH change, its easy magnetization axis also switches from in-plane to out-of-plane. The switchable electrical control of heterostructures by ferroelectric Ga<sub>2</sub>O<sub>3</sub> is nonvolatile. These findings are important for understanding ferroelectric control of spintronics and electromagnetic coupling and provide a potential route for developing multiferroic memory devices.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, metal halide compounds have been widely studied as a class of semiconductor materials with superior optoelectronic characteristics. In particular, rare metal doping has been observed to affect the properties of metal halide compounds, yet the mechanisms are not understood. In this study, we incorporated Eu³⁺ into the Cs₂FeCl₅·H₂O crystal system, aiming to thoroughly investigate its comprehensive effects on the material's structural, optical, and electrical properties, and ultimate performance as a photodetector. The results indicate that both the Cs₂FeCl₅·H₂O and Eu doping Cs₂FeCl₅·H₂O single crystals belong to the orthorhombic crystal system with the space group Cmcm (No.63). The Eu3+ ion is successfully incorporated into the host lattice, which result in the lattice expansion phenomenon observed in X-ray Diffraction (XRD), bandgap widening, increasing the resistance and emission intensity of the samples in photoluminescence. This positive outcome is attributed to the effective passivation realized by Eu3+ incorporation. The dark current density of the photodetector devices based on the Eu3+- doping decreased significantly from the undoped value of 18.3 ± 3.0 to 2.1 ± 1.2 μA/cm². Smaller dark current and high bulk resistance can effectively prevent semiconductor devices from breakdown, making them applicable in the field of high-power semiconductors. This work offers insight for the future design and development of metal halide photoelectronic materials with low noise and high response speed.
{"title":"Eu³⁺-induced passivation and charge-transport modulation in Cs₂FeCl₅·H₂O single crystals and evaporated thin films for photodetectors","authors":"Chen Wang, Yu Li, Jiayi Ren, Huimeng Shen, Qi Sun, Hui Yan, Xinpei Li, Huawei Zhou, Xianxi Zhang, Federico Rosei, Jun Zhang","doi":"10.1039/d5cp04307g","DOIUrl":"https://doi.org/10.1039/d5cp04307g","url":null,"abstract":"In recent years, metal halide compounds have been widely studied as a class of semiconductor materials with superior optoelectronic characteristics. In particular, rare metal doping has been observed to affect the properties of metal halide compounds, yet the mechanisms are not understood. In this study, we incorporated Eu³⁺ into the Cs₂FeCl₅·H₂O crystal system, aiming to thoroughly investigate its comprehensive effects on the material's structural, optical, and electrical properties, and ultimate performance as a photodetector. The results indicate that both the Cs₂FeCl₅·H₂O and Eu doping Cs₂FeCl₅·H₂O single crystals belong to the orthorhombic crystal system with the space group Cmcm (No.63). The Eu3+ ion is successfully incorporated into the host lattice, which result in the lattice expansion phenomenon observed in X-ray Diffraction (XRD), bandgap widening, increasing the resistance and emission intensity of the samples in photoluminescence. This positive outcome is attributed to the effective passivation realized by Eu3+ incorporation. The dark current density of the photodetector devices based on the Eu3+- doping decreased significantly from the undoped value of 18.3 ± 3.0 to 2.1 ± 1.2 μA/cm². Smaller dark current and high bulk resistance can effectively prevent semiconductor devices from breakdown, making them applicable in the field of high-power semiconductors. This work offers insight for the future design and development of metal halide photoelectronic materials with low noise and high response speed.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"33 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
NaNiO2 is a layered material composed of alternating NaO6 and NiO6 octahedra, which undergoes an insulator-metal transition (IMT) from a monoclinic insulating phase to a metallic phase at approximately 480 K. Although this phase transition has been experimentally observed, its microscopic mechanism remains unclear, particularly regarding the role of Jahn-Teller (JT) distortion and the nature of the structural dynamics during the transition. In this work, we carry out a comprehensive first-principles study to address these issues. Our results show that the IMT is primarily driven by the gradual disappearance of the JT distortion of Ni3+, which restores the eg orbital degeneracy and enables electronic delocalization. Furthermore, potential energy surface analysis and phonon spectrum calculations reveal that this process follows a displacive phase transition pathway, consistent with experimental observations. These findings provide, for the first time, a theoretical explanation of the microscopic mechanism underlying the IMT in NaNiO2, thereby clarifying its structural-electronic interplay and offering new insights into the phase transition behavior of transition-metal oxides for future material applications.
{"title":"First-principles investigation of the insulator-metal transition in layered NaNiO<sub>2</sub>: coupled electronic and lattice effects.","authors":"Xiaohong Chu, Zhenyi Jiang, Ping Guo, Jiming Zheng, Xiaodong Zhang","doi":"10.1039/d5cp03746h","DOIUrl":"https://doi.org/10.1039/d5cp03746h","url":null,"abstract":"<p><p>NaNiO<sub>2</sub> is a layered material composed of alternating NaO<sub>6</sub> and NiO<sub>6</sub> octahedra, which undergoes an insulator-metal transition (IMT) from a monoclinic insulating phase to a metallic phase at approximately 480 K. Although this phase transition has been experimentally observed, its microscopic mechanism remains unclear, particularly regarding the role of Jahn-Teller (JT) distortion and the nature of the structural dynamics during the transition. In this work, we carry out a comprehensive first-principles study to address these issues. Our results show that the IMT is primarily driven by the gradual disappearance of the JT distortion of Ni<sup>3+</sup>, which restores the e<sub>g</sub> orbital degeneracy and enables electronic delocalization. Furthermore, potential energy surface analysis and phonon spectrum calculations reveal that this process follows a displacive phase transition pathway, consistent with experimental observations. These findings provide, for the first time, a theoretical explanation of the microscopic mechanism underlying the IMT in NaNiO<sub>2</sub>, thereby clarifying its structural-electronic interplay and offering new insights into the phase transition behavior of transition-metal oxides for future material applications.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Henry Nicole González-Ramírez, Zeferino Gómez-Sandoval, Gururaj Kudur Jayaprakash, Juan Pablo Mojica-Sánchez, Roberto Flores-Moreno, Kayim Pineda-Urbina
In this study, we explored the energetic, structural, and magnetic properties of yttrium-doped lithium and potassium clusters using density functional theory combined with Born–Oppenheimer molecular dynamics simulations. The analysis revealed magnetic superatoms such as K9Y2 (μ = 5μB) with a frontier configuration analogous to Fe+. Global reactivity descriptors, particularly the low hardness values (η), identified K12Y, K11Y2, and K13 as the most reactive potassium clusters, while the analogous Li12Y, Li11Y2, and Li13 were also selected for subsequent hydrogen interaction analyses. The most stable hydrogen–cluster structures extracted from Born–Oppenheimer molecular dynamics at 300 K were reoptimized including dispersion corrections to compute adsorption and Gibbs free energies. The resulting complexes were analyzed through QTAIM, ELF, and Laplacian electron density maps, complemented by CM5 charge analysis. These results reveal predominant molecular physisorption across the Y-doped systems, with localized polarized chemisorption only in Li12Y. Overall, yttrium doping enhances magnetic polarization, energetic stability, and structural resilience of alkali-metal clusters, which retain their superatomic character and near-icosahedral frameworks under hydrogen exposure.
{"title":"Yttrium-doped lithium and potassium clusters: magnetic superatoms and their interaction with hydrogen","authors":"Henry Nicole González-Ramírez, Zeferino Gómez-Sandoval, Gururaj Kudur Jayaprakash, Juan Pablo Mojica-Sánchez, Roberto Flores-Moreno, Kayim Pineda-Urbina","doi":"10.1039/d5cp04393j","DOIUrl":"https://doi.org/10.1039/d5cp04393j","url":null,"abstract":"In this study, we explored the energetic, structural, and magnetic properties of yttrium-doped lithium and potassium clusters using density functional theory combined with Born–Oppenheimer molecular dynamics simulations. The analysis revealed magnetic superatoms such as K<small><sub>9</sub></small>Y<small><sub>2</sub></small> (<em>μ</em> = 5<em>μ</em><small><sub>B</sub></small>) with a frontier configuration analogous to Fe<small><sup>+</sup></small>. Global reactivity descriptors, particularly the low hardness values (<em>η</em>), identified K<small><sub>12</sub></small>Y, K<small><sub>11</sub></small>Y<small><sub>2</sub></small>, and K<small><sub>13</sub></small> as the most reactive potassium clusters, while the analogous Li<small><sub>12</sub></small>Y, Li<small><sub>11</sub></small>Y<small><sub>2</sub></small>, and Li<small><sub>13</sub></small> were also selected for subsequent hydrogen interaction analyses. The most stable hydrogen–cluster structures extracted from Born–Oppenheimer molecular dynamics at 300 K were reoptimized including dispersion corrections to compute adsorption and Gibbs free energies. The resulting complexes were analyzed through QTAIM, ELF, and Laplacian electron density maps, complemented by CM5 charge analysis. These results reveal predominant molecular physisorption across the Y-doped systems, with localized polarized chemisorption only in Li<small><sub>12</sub></small>Y. Overall, yttrium doping enhances magnetic polarization, energetic stability, and structural resilience of alkali-metal clusters, which retain their superatomic character and near-icosahedral frameworks under hydrogen exposure.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"72 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuxue Zhao, Linlin Wu, Liangkai Xu, Rui Zou, Chang-Jun Liu
Supported gold catalysts are fundamentally and practically important for hydrogenation reactions due to their unique electronic properties and catalytic activity. In this work, Au nanoparticles were successfully deposited onto an In2O3 support via a deposition-precipitation method to form a Au/In2O3 catalyst, which was subsequently evaluated for CO2 hydrogenation under atmospheric pressure. This catalyst exhibits outstanding low-temperature activity for the reverse water gas shift (RWGS) reaction, achieving a CO2 conversion of 21.3%, a CO selectivity of 100%, and a CO formation rate of 0.30 mmolCO gcat-1 min-1 at 350 °C. Characterization results reveal that Au nanoparticles are uniformly dispersed on the In2O3 surface, accompanied by charge transfer from Au to the In2O3 support. This strong electronic metal-support interaction (EMSI) results in the formation of positively charged Auδ+ species, which facilitates H2 dissociation. Meanwhile, the generation of surface oxygen vacancies on In2O3 is promoted, enhancing CO2 adsorption and activation. These synergistic effects between Au nanoparticles and In2O3 account for the superior RWGS activities of the Au/In2O3 catalyst.
{"title":"A highly active Au/In<sub>2</sub>O<sub>3</sub> catalyst for the reverse water gas shift reaction.","authors":"Yuxue Zhao, Linlin Wu, Liangkai Xu, Rui Zou, Chang-Jun Liu","doi":"10.1039/d5cp04442a","DOIUrl":"https://doi.org/10.1039/d5cp04442a","url":null,"abstract":"<p><p>Supported gold catalysts are fundamentally and practically important for hydrogenation reactions due to their unique electronic properties and catalytic activity. In this work, Au nanoparticles were successfully deposited onto an In<sub>2</sub>O<sub>3</sub> support <i>via</i> a deposition-precipitation method to form a Au/In<sub>2</sub>O<sub>3</sub> catalyst, which was subsequently evaluated for CO<sub>2</sub> hydrogenation under atmospheric pressure. This catalyst exhibits outstanding low-temperature activity for the reverse water gas shift (RWGS) reaction, achieving a CO<sub>2</sub> conversion of 21.3%, a CO selectivity of 100%, and a CO formation rate of 0.30 mmol<sub>CO</sub> g<sub>cat</sub><sup>-1</sup> min<sup>-1</sup> at 350 °C. Characterization results reveal that Au nanoparticles are uniformly dispersed on the In<sub>2</sub>O<sub>3</sub> surface, accompanied by charge transfer from Au to the In<sub>2</sub>O<sub>3</sub> support. This strong electronic metal-support interaction (EMSI) results in the formation of positively charged Au<sup><i>δ</i>+</sup> species, which facilitates H<sub>2</sub> dissociation. Meanwhile, the generation of surface oxygen vacancies on In<sub>2</sub>O<sub>3</sub> is promoted, enhancing CO<sub>2</sub> adsorption and activation. These synergistic effects between Au nanoparticles and In<sub>2</sub>O<sub>3</sub> account for the superior RWGS activities of the Au/In<sub>2</sub>O<sub>3</sub> catalyst.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hayden A Moran, Abigail F. Moody, Mark A Boyer, Paul Garrett, Manuel Quiroz, Sarnali Sanfui, Marcetta Y. Darensbourg, Carlos Baiz, Daniel P. Tabor
Two-dimensional infrared spectroscopy offers unique capabilities for probing vibrational coupling in complex metal–ligand systems. In this paper, we combine two-dimensional infrared spectroscopy with vibrational perturbation theory to investigate vibrational coupling in a diiron trinitrosyl complex across three stable redox states. Although these systems are challenging for electronic structure methods, we demonstrate that key features of experimental 2D IR spectra can be accurately reproduced using reduced-dimensional anharmonic calculations with a small harmonic frequency scaling. Analysis reveals that N–O stretching modes maintain high locality across all redox states, with coupling patterns that directly reflect variations in Fe–N bond strength. Using curvilinear coordinate analysis, we demonstrate that these differences result from systematic changes in cubic anharmonic force constants rather than mode delocalization. Our results establish N–O stretches as sensitive probes of metal–ligand bonding strength, expanding the toolkit for studying biologically relevant nitrosyl complexes.
{"title":"Low-Cost Calculation and Analysis of 2D IR Spectra of Model Diiron Trinitrosyl Complexes in the NO Stretch Region with Vibrational Perturbation Theory","authors":"Hayden A Moran, Abigail F. Moody, Mark A Boyer, Paul Garrett, Manuel Quiroz, Sarnali Sanfui, Marcetta Y. Darensbourg, Carlos Baiz, Daniel P. Tabor","doi":"10.1039/d5cp03578c","DOIUrl":"https://doi.org/10.1039/d5cp03578c","url":null,"abstract":"Two-dimensional infrared spectroscopy offers unique capabilities for probing vibrational coupling in complex metal–ligand systems. In this paper, we combine two-dimensional infrared spectroscopy with vibrational perturbation theory to investigate vibrational coupling in a diiron trinitrosyl complex across three stable redox states. Although these systems are challenging for electronic structure methods, we demonstrate that key features of experimental 2D IR spectra can be accurately reproduced using reduced-dimensional anharmonic calculations with a small harmonic frequency scaling. Analysis reveals that N–O stretching modes maintain high locality across all redox states, with coupling patterns that directly reflect variations in Fe–N bond strength. Using curvilinear coordinate analysis, we demonstrate that these differences result from systematic changes in cubic anharmonic force constants rather than mode delocalization. Our results establish N–O stretches as sensitive probes of metal–ligand bonding strength, expanding the toolkit for studying biologically relevant nitrosyl complexes.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"7 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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