Jocasta Ávila, Daniel Lozano-Martín, Mirella Simões Santos, Yunxiao Zhang, Hua Li, Agilio Pádua, Rob Atkin, Margarida Costa Gomes
Surface active ionic liquids (SAILs) combine useful characteristics of both ionic liquids (ILs) and surfactants, hence are promising candidates for a wide range of applications. However, the effect of SAIL ionic structures on their physicochemical properties remains unclear, which limits their uptake. To address this knowledge gap, in this work we investigated the density, viscosity, surface tension, and corresponding critical micelle concentration in water, as well as gas absorption of SAILs with a variety of cation and anion structures. SAILs containing anions with linear alkyl chains have smaller molar volumes than those with branched alkyl chains, because linear alkyl chains are interdigitated to a greater extent, leading to more compact packing. This interdigitation also results in SAILs being about two orders of magnitude more viscous than comparable conventional ILs. SAILs at the liquid-air interface orient alkyl chains towards the air, leading to low surface tensions closer to n-alkanes than conventional ILs. Critical temperatures of about 900 K could be estimated for all SAILs from their surface tensions. When dissolved in water, SAILs adsorb at the liquid-air interface and lower the surface tension, like conventional surfactants in water, after which micelles form. Molecular simulations show that the micelles are spherical and that lower critical micelle concentrations correspond to the formation of aggregates with a larger number of ion pairs. $mathrm{CO_{2}}$ and $mathrm{N_{2}}$ absorption capacities are examined and we conclude that ionic liquids with larger non-polar domains absorb larger quantities of both gases.
{"title":"Effect of ion structure on the physicochemical properties and gas absorption of surface active ionic liquids","authors":"Jocasta Ávila, Daniel Lozano-Martín, Mirella Simões Santos, Yunxiao Zhang, Hua Li, Agilio Pádua, Rob Atkin, Margarida Costa Gomes","doi":"arxiv-2409.11853","DOIUrl":"https://doi.org/arxiv-2409.11853","url":null,"abstract":"Surface active ionic liquids (SAILs) combine useful characteristics of both\u0000ionic liquids (ILs) and surfactants, hence are promising candidates for a wide\u0000range of applications. However, the effect of SAIL ionic structures on their\u0000physicochemical properties remains unclear, which limits their uptake. To\u0000address this knowledge gap, in this work we investigated the density,\u0000viscosity, surface tension, and corresponding critical micelle concentration in\u0000water, as well as gas absorption of SAILs with a variety of cation and anion\u0000structures. SAILs containing anions with linear alkyl chains have smaller molar\u0000volumes than those with branched alkyl chains, because linear alkyl chains are\u0000interdigitated to a greater extent, leading to more compact packing. This\u0000interdigitation also results in SAILs being about two orders of magnitude more\u0000viscous than comparable conventional ILs. SAILs at the liquid-air interface\u0000orient alkyl chains towards the air, leading to low surface tensions closer to\u0000n-alkanes than conventional ILs. Critical temperatures of about 900 K could be\u0000estimated for all SAILs from their surface tensions. When dissolved in water,\u0000SAILs adsorb at the liquid-air interface and lower the surface tension, like\u0000conventional surfactants in water, after which micelles form. Molecular\u0000simulations show that the micelles are spherical and that lower critical\u0000micelle concentrations correspond to the formation of aggregates with a larger\u0000number of ion pairs. $mathrm{CO_{2}}$ and $mathrm{N_{2}}$ absorption\u0000capacities are examined and we conclude that ionic liquids with larger\u0000non-polar domains absorb larger quantities of both gases.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael Gatchell, Raka Paul, MingChao Ji, Stefan Rosén, Richard D. Thomas, Henrik Cederquist, Henning T. Schmidt, Åsa Larson, Henning Zettergren
Context: Mutual neutralization between cations and anions play an important role in determining the charge-balance in certain astrophysical environments. However, empirical data for such reactions involving complex molecular species has been lacking due to challenges in performing experimental studies, leaving the astronomical community to rely on decades old models with large uncertainties for describing these processes in the interstellar medium. Aims: To investigate the mutual neutralization (MN) reaction, C$_{60}^+$ + C$_{60}^-$ $rightarrow$ C$_{60}^*$ + C$_{60}$, for collisions at interstellar-like conditions. Methods: The mutual neutralization reaction between C$_{60}^+$ and C$_{60}^-$ at collision energies of 100,meV was studied using the Double ElectroStatic Ion Ring ExpEriment, DESIREE, and its merged-beam capabilities. To aid in the interpretation of the experimental results, semi-classical modeling based on the Landau-Zener approach was performed for the studied reaction. Results: We experimentally identify a narrow range of kinetic energies for the neutral reaction products. Modeling was used to calculate the quantum state-selective reaction probabilities, absolute cross sections, and rate coefficients of these MN reactions, using the experimental results as a benchmark. The MN cross sections are compared with model results for electron attachment to C$_{60}$ and electron recombination with C$_{60}^+$. Conclusions: The present results show that it is crucial to take mutual polarization effects, the finite sizes, and the final quantum states of both molecular ions into account for reliable predictions of MN rates expected to strongly influence the charge-balance and chemistry in, e.g., dense molecular clouds.
{"title":"Mutual neutralization of C$_{60}^+$ and C$_{60}^-$ ions: Excitation energies and state-selective rate coefficients","authors":"Michael Gatchell, Raka Paul, MingChao Ji, Stefan Rosén, Richard D. Thomas, Henrik Cederquist, Henning T. Schmidt, Åsa Larson, Henning Zettergren","doi":"arxiv-2409.11851","DOIUrl":"https://doi.org/arxiv-2409.11851","url":null,"abstract":"Context: Mutual neutralization between cations and anions play an important\u0000role in determining the charge-balance in certain astrophysical environments.\u0000However, empirical data for such reactions involving complex molecular species\u0000has been lacking due to challenges in performing experimental studies, leaving\u0000the astronomical community to rely on decades old models with large\u0000uncertainties for describing these processes in the interstellar medium. Aims:\u0000To investigate the mutual neutralization (MN) reaction, C$_{60}^+$ + C$_{60}^-$\u0000$rightarrow$ C$_{60}^*$ + C$_{60}$, for collisions at interstellar-like\u0000conditions. Methods: The mutual neutralization reaction between C$_{60}^+$ and\u0000C$_{60}^-$ at collision energies of 100,meV was studied using the Double\u0000ElectroStatic Ion Ring ExpEriment, DESIREE, and its merged-beam capabilities.\u0000To aid in the interpretation of the experimental results, semi-classical\u0000modeling based on the Landau-Zener approach was performed for the studied\u0000reaction. Results: We experimentally identify a narrow range of kinetic\u0000energies for the neutral reaction products. Modeling was used to calculate the\u0000quantum state-selective reaction probabilities, absolute cross sections, and\u0000rate coefficients of these MN reactions, using the experimental results as a\u0000benchmark. The MN cross sections are compared with model results for electron\u0000attachment to C$_{60}$ and electron recombination with C$_{60}^+$. Conclusions:\u0000The present results show that it is crucial to take mutual polarization\u0000effects, the finite sizes, and the final quantum states of both molecular ions\u0000into account for reliable predictions of MN rates expected to strongly\u0000influence the charge-balance and chemistry in, e.g., dense molecular clouds.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daniel Timmer, Daniel C. Lünemann, Moritz Gittinger, Antonietta De Sio, Cristian Manzoni, Giulio Cerullo, Christoph Lienau
Selecting distinct quantum pathways in two-dimensional electronic spectroscopy (2DES) can give particularly deep insights into coherent and incoherent interactions and quantum dynamics in various materials. This includes isolating rephasing and non-rephasing pathways for conventional single-quantum 2DES, but also the ability to record double- and zero-quantum spectra. Such advanced 2DES schemes usually require phase-cycling when performed in a partially or fully collinear geometry. A particularly simple and effective implementation of 2DES utilizes an in-line birefringent interferometer, the Translating-Wedge-based Identical pulses eNcoding System (TWINS), for the generation of an inherently phase-stable collinear excitation pulse pair. Here, we demonstrate how the TWINS can be adapted to allow for phase-cycling and experimental access to isolated quantum pathways. These new capabilities are demonstrated by recording rephasing, non-rephasing, zero-quantum and double-quantum 2DES on a molecular J-aggregate. This easy-to-implement extension opens up new experimental possibilities for TWINS-based 2DES in multidimensional all-optical and photoemission spectroscopy and microscopy.
{"title":"Phase-cycling and double-quantum two-dimensional electronic spectroscopy using a common-path birefringent interferometer","authors":"Daniel Timmer, Daniel C. Lünemann, Moritz Gittinger, Antonietta De Sio, Cristian Manzoni, Giulio Cerullo, Christoph Lienau","doi":"arxiv-2409.11959","DOIUrl":"https://doi.org/arxiv-2409.11959","url":null,"abstract":"Selecting distinct quantum pathways in two-dimensional electronic\u0000spectroscopy (2DES) can give particularly deep insights into coherent and\u0000incoherent interactions and quantum dynamics in various materials. This\u0000includes isolating rephasing and non-rephasing pathways for conventional\u0000single-quantum 2DES, but also the ability to record double- and zero-quantum\u0000spectra. Such advanced 2DES schemes usually require phase-cycling when\u0000performed in a partially or fully collinear geometry. A particularly simple and\u0000effective implementation of 2DES utilizes an in-line birefringent\u0000interferometer, the Translating-Wedge-based Identical pulses eNcoding System\u0000(TWINS), for the generation of an inherently phase-stable collinear excitation\u0000pulse pair. Here, we demonstrate how the TWINS can be adapted to allow for\u0000phase-cycling and experimental access to isolated quantum pathways. These new\u0000capabilities are demonstrated by recording rephasing, non-rephasing,\u0000zero-quantum and double-quantum 2DES on a molecular J-aggregate. This\u0000easy-to-implement extension opens up new experimental possibilities for\u0000TWINS-based 2DES in multidimensional all-optical and photoemission spectroscopy\u0000and microscopy.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"73 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mengting Zhou, Hongxia Liu, Juntao Yan, Qingjun Chen, Rong Chen, Lei Liu
Metallic bismuth is both non-toxic and cost-effective. Bi-based catalysts have demonstrated the ability to efficiently produce HCOOH through CO2RR while effectively inhibiting the HER. Although many experiments have been reported concerning its performance towards CO2 reduction, the impact its valence states and crystal faces on CO2RR selectivity (e.g. HCOOH versus CO) it still under debate. Here, we performed a comprehensive study via density functional theory, by including three typical valence states of Bi, such as 0 (Bi), +3 (Bi2O3) and +5 (Bi2O5), as well as their often-studied crystal facets. The results show that metallic Bi demonstrates a poor selectivity for HCOOH, but boasts a higher conversion rate for CO2. While Bi2O3 exhibits a good selectivity for HCOOH production, yet it displays a lower conversion rate for CO2. For Bi2O5, all studied surfaces show high energy barriers in both cases of HCOOH and CO production, and lower energy barriers for HER reactions, indicating that Bi at +5 valence state is not the good choice for 2e transfer reactions. Subsequently, we further examined the effects of oxygen contents on the selectivity of HCOOH and the conversion rate for CO2. Interestingly, we found that partial oxidization of Bi benefits both the selectivity and the conversion rate. With these observations, we suggest that a mixture of Bi (0) and Bi2O3 (+3) phases would be a better choice than single crystals for future experiments.
金属铋既无毒又具有成本效益。铋基催化剂已证明能够通过 CO2RR 高效地产生 HCOOH，同时有效抑制 HER。虽然已有许多关于其 CO2 还原性能的实验报告，但其价态和晶面对 CO2RR 选择性（如 HCOOH 与 CO）的影响仍有待商榷。在这里，我们通过密度泛函理论进行了全面研究，包括 Bi 的三种典型价态，如 0（Bi）、+3（Bi2O3）和+5（Bi2O5），以及经常研究的晶面。研究结果表明，金属 Bi 对 HCOOH 的选择性较差，但对 CO2 的转化率较高。Bi2O3 对 HCOOH 的生成具有良好的选择性，但对 CO2 的转化率较低。对于 Bi2O5，所有研究的表面在 HCOOH 和 CO 生成两种情况下都显示出较高的能垒，而在 HER 反应中则显示出较低的能垒，这表明+5 价态的 Bi 不是 2e 转移反应的良好选择。有趣的是，我们发现 Bi 的部分氧化对选择性和转化率都有好处。根据这些观察结果，我们认为在未来的实验中，Bi (0) 和 Bi2O3(+3) 的混合物将是比单晶体更好的选择。
{"title":"On the electrochemical CO2 reduction by Bi-based catalysts: single crystals or mixture phases","authors":"Mengting Zhou, Hongxia Liu, Juntao Yan, Qingjun Chen, Rong Chen, Lei Liu","doi":"arxiv-2409.11648","DOIUrl":"https://doi.org/arxiv-2409.11648","url":null,"abstract":"Metallic bismuth is both non-toxic and cost-effective. Bi-based catalysts\u0000have demonstrated the ability to efficiently produce HCOOH through CO2RR while\u0000effectively inhibiting the HER. Although many experiments have been reported\u0000concerning its performance towards CO2 reduction, the impact its valence states\u0000and crystal faces on CO2RR selectivity (e.g. HCOOH versus CO) it still under\u0000debate. Here, we performed a comprehensive study via density functional theory,\u0000by including three typical valence states of Bi, such as 0 (Bi), +3 (Bi2O3) and\u0000+5 (Bi2O5), as well as their often-studied crystal facets. The results show\u0000that metallic Bi demonstrates a poor selectivity for HCOOH, but boasts a higher\u0000conversion rate for CO2. While Bi2O3 exhibits a good selectivity for HCOOH\u0000production, yet it displays a lower conversion rate for CO2. For Bi2O5, all\u0000studied surfaces show high energy barriers in both cases of HCOOH and CO\u0000production, and lower energy barriers for HER reactions, indicating that Bi at\u0000+5 valence state is not the good choice for 2e transfer reactions.\u0000Subsequently, we further examined the effects of oxygen contents on the\u0000selectivity of HCOOH and the conversion rate for CO2. Interestingly, we found\u0000that partial oxidization of Bi benefits both the selectivity and the conversion\u0000rate. With these observations, we suggest that a mixture of Bi (0) and Bi2O3\u0000(+3) phases would be a better choice than single crystals for future\u0000experiments.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Machine learning (ML) potentials typically target a single quantum chemical (QC) level while the ML models developed for multi-fidelity learning have not been shown to provide scalable solutions for foundational models. Here we introduce the all-in-one (AIO) ANI model architecture based on multimodal learning which can learn an arbitrary number of QC levels. Our all-in-one learning approach offers a more general and easier-to-use alternative to transfer learning. We use it to train the AIO-ANI-UIP foundational model with the generalization capability comparable to semi-empirical GFN2-xTB and DFT with a double-zeta basis set for organic molecules. We show that the AIO-ANI model can learn across different QC levels ranging from semi-empirical to density functional theory to coupled cluster. We also use AIO models to design the foundational model {Delta}-AIO-ANI based on {Delta}-learning with increased accuracy and robustness compared to AIO-ANI-UIP. The code and the foundational models are available at https://github.com/dralgroup/aio-ani; they will be integrated into the universal and updatable AI-enhanced QM (UAIQM) library and made available in the MLatom package so that they can be used online at the XACS cloud computing platform (see https://github.com/dralgroup/mlatom for updates).
{"title":"All-in-one foundational models learning across quantum chemical levels","authors":"Yuxinxin Chen, Pavlo O. Dral","doi":"arxiv-2409.12015","DOIUrl":"https://doi.org/arxiv-2409.12015","url":null,"abstract":"Machine learning (ML) potentials typically target a single quantum chemical\u0000(QC) level while the ML models developed for multi-fidelity learning have not\u0000been shown to provide scalable solutions for foundational models. Here we\u0000introduce the all-in-one (AIO) ANI model architecture based on multimodal\u0000learning which can learn an arbitrary number of QC levels. Our all-in-one\u0000learning approach offers a more general and easier-to-use alternative to\u0000transfer learning. We use it to train the AIO-ANI-UIP foundational model with\u0000the generalization capability comparable to semi-empirical GFN2-xTB and DFT\u0000with a double-zeta basis set for organic molecules. We show that the AIO-ANI\u0000model can learn across different QC levels ranging from semi-empirical to\u0000density functional theory to coupled cluster. We also use AIO models to design\u0000the foundational model {Delta}-AIO-ANI based on {Delta}-learning with\u0000increased accuracy and robustness compared to AIO-ANI-UIP. The code and the\u0000foundational models are available at https://github.com/dralgroup/aio-ani; they\u0000will be integrated into the universal and updatable AI-enhanced QM (UAIQM)\u0000library and made available in the MLatom package so that they can be used\u0000online at the XACS cloud computing platform (see\u0000https://github.com/dralgroup/mlatom for updates).","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a novel route to constructing cost-efficient semi-empirical approximations for the non-additive kinetic energy in subsystem density functional theory. The developed methodology is based on the use of Slater determinants composed of non-orthogonal Kohn$unicode{x2013}$Sham-like orbitals for the evaluation of kinetic energy expectation values and the expansion of the inverse molecular-orbital overlap matrix into a Neumann series. Applying these techniques, we derived and implemented a series of orbital-dependent approximations for the non-additive kinetic energy, which are employed self-consistently. Our proof-of-principle computations demonstrated quantitatively correct results for potential energy curves and electron densities and hinted on the applicability of the introduced empirical parameters to different types of molecular systems and intermolecular interactions. We therefore conclude that the presented study is an important step towards constructing accurate and efficient orbital-dependent approximations for the non-additive kinetic energy applicable to large molecular systems.
{"title":"Developing Orbital-Dependent Corrections for the Non-Additive Kinetic Energy in Subsystem Density Functional Theory","authors":"Larissa Sophie Eitelhuber, Denis G. Artiukhin","doi":"arxiv-2409.11914","DOIUrl":"https://doi.org/arxiv-2409.11914","url":null,"abstract":"We present a novel route to constructing cost-efficient semi-empirical\u0000approximations for the non-additive kinetic energy in subsystem density\u0000functional theory. The developed methodology is based on the use of Slater\u0000determinants composed of non-orthogonal Kohn$unicode{x2013}$Sham-like orbitals\u0000for the evaluation of kinetic energy expectation values and the expansion of\u0000the inverse molecular-orbital overlap matrix into a Neumann series. Applying\u0000these techniques, we derived and implemented a series of orbital-dependent\u0000approximations for the non-additive kinetic energy, which are employed\u0000self-consistently. Our proof-of-principle computations demonstrated\u0000quantitatively correct results for potential energy curves and electron\u0000densities and hinted on the applicability of the introduced empirical\u0000parameters to different types of molecular systems and intermolecular\u0000interactions. We therefore conclude that the presented study is an important\u0000step towards constructing accurate and efficient orbital-dependent\u0000approximations for the non-additive kinetic energy applicable to large\u0000molecular systems.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fernando Hevia, Juan Antonio González, Ana Cobos, Isaías García de la Fuente, Cristina Alonso Tristán
Relative permittivities at 1 MHz, $varepsilon_{text{r}}$, and refractive indices at the sodium D-line, $n_{text{D}}$, are reported at 0.1 MPa and at (293.15-303.15) K for the binary systems 1-alkanol + n-hexylamine (HxA). Also, their corresponding excess functions are calculated and correlated. Positive values of the excess permittivities, $varepsilon_{text{r}}^{text{E}}$, are encountered for the methanol system, whereas the remaining mixtures show negative values. This reveals that interactions between unlike molecules contribute positively to $varepsilon_{text{r}}^{text{E}}$. This contribution is dominant for the methanol mixture, while those arising from the breaking of interactions between like molecules are prevalent for the remaining mixtures. At ${phi}_1$ (volume fraction) = 0.5, $varepsilon_{text{r}}^{text{E}}$ changes in the order: methanol > 1-propanol > 1-butanol > 1-pentanol < 1-heptanol. Similar variation with the chain length of the 1-alkanol is observed for mixtures such as 1-alkanol + heptane, or + cyclohexylamine, and can be explained in terms of the lower and weaker self-association of longer 1-alkanols. The effect of the replacement of HxA by cyclohexylamine, or by aniline, is also shown. Calculations on molar refractions indicate that dispersive interactions in the systems under study increase with the length of the 1-alkanol. The mixtures are studied by means of the application of the Kirkwood-Fr"ohlich model, and the Kirkwood correlation factors, including the corresponding excess values, are reported.
{"title":"Thermodynamics of mixtures with strongly negative deviations from Raoult's law. XV. Permittivities and refractive indices for 1-alkanol + n-hexylamine systems at (293.15-303.15) K. Application of the Kirkwood-Fröhlich model","authors":"Fernando Hevia, Juan Antonio González, Ana Cobos, Isaías García de la Fuente, Cristina Alonso Tristán","doi":"arxiv-2409.11801","DOIUrl":"https://doi.org/arxiv-2409.11801","url":null,"abstract":"Relative permittivities at 1 MHz, $varepsilon_{text{r}}$, and refractive\u0000indices at the sodium D-line, $n_{text{D}}$, are reported at 0.1 MPa and at\u0000(293.15-303.15) K for the binary systems 1-alkanol + n-hexylamine (HxA). Also,\u0000their corresponding excess functions are calculated and correlated. Positive\u0000values of the excess permittivities, $varepsilon_{text{r}}^{text{E}}$, are\u0000encountered for the methanol system, whereas the remaining mixtures show\u0000negative values. This reveals that interactions between unlike molecules\u0000contribute positively to $varepsilon_{text{r}}^{text{E}}$. This contribution\u0000is dominant for the methanol mixture, while those arising from the breaking of\u0000interactions between like molecules are prevalent for the remaining mixtures.\u0000At ${phi}_1$ (volume fraction) = 0.5, $varepsilon_{text{r}}^{text{E}}$\u0000changes in the order: methanol > 1-propanol > 1-butanol > 1-pentanol <\u00001-heptanol. Similar variation with the chain length of the 1-alkanol is\u0000observed for mixtures such as 1-alkanol + heptane, or + cyclohexylamine, and\u0000can be explained in terms of the lower and weaker self-association of longer\u00001-alkanols. The effect of the replacement of HxA by cyclohexylamine, or by\u0000aniline, is also shown. Calculations on molar refractions indicate that\u0000dispersive interactions in the systems under study increase with the length of\u0000the 1-alkanol. The mixtures are studied by means of the application of the\u0000Kirkwood-Fr\"ohlich model, and the Kirkwood correlation factors, including the\u0000corresponding excess values, are reported.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rei Ogawa, Hiroki Kusudo, Takeshi Omori, Edward R. Smith, Laurent Joly, Samy Merabia, Yasutaka Yamaguchi
In this study, we carried out equilibrium molecular dynamics (EMD) simulations of the liquid-liquid interface between two different Lennard-Jones components with varying miscibility, where we examined the relation between the interfacial tension and isolation free energy using both a mechanical and thermodynamic approach. Using the mechanical approach, we obtained a stress distribution around a quasi-one-dimensional (1D) EMD systems with a flat LL interface. From the stress distribution, we calculated the liquid-liquid interfacial tension based on Bakker's equation, which uses the stress anisotropy around the interface, and measures how it varies with miscibility. The second approach uses thermodynamic integration by enforcing quasi-static isolation of the two liquids to calculate the free energy. This uses the same EMD systems as the mechanical approach, with both extended dry-surface and phantom-wall (PW) schemes applied. When the two components were immiscible, the interfacial tension and isolation free energy were in good agreement, provided all kinetic and interaction contributions were included in the stress. When the components were miscible, the values were significantly different. From the result of PW for the case of completely mixed liquids, the difference was attributed to the additional free energy required to separate the binary mixture into single components against the osmotic pressure prior to the complete detachment of the two components, i.e., the free energy of mixing.
{"title":"Mechanical and thermodynamic routes to the liquid-liquid interfacial tension and mixing free energy by molecular dynamics","authors":"Rei Ogawa, Hiroki Kusudo, Takeshi Omori, Edward R. Smith, Laurent Joly, Samy Merabia, Yasutaka Yamaguchi","doi":"arxiv-2409.10856","DOIUrl":"https://doi.org/arxiv-2409.10856","url":null,"abstract":"In this study, we carried out equilibrium molecular dynamics (EMD)\u0000simulations of the liquid-liquid interface between two different Lennard-Jones\u0000components with varying miscibility, where we examined the relation between the\u0000interfacial tension and isolation free energy using both a mechanical and\u0000thermodynamic approach. Using the mechanical approach, we obtained a stress\u0000distribution around a quasi-one-dimensional (1D) EMD systems with a flat LL\u0000interface. From the stress distribution, we calculated the liquid-liquid\u0000interfacial tension based on Bakker's equation, which uses the stress\u0000anisotropy around the interface, and measures how it varies with miscibility.\u0000The second approach uses thermodynamic integration by enforcing quasi-static\u0000isolation of the two liquids to calculate the free energy. This uses the same\u0000EMD systems as the mechanical approach, with both extended dry-surface and\u0000phantom-wall (PW) schemes applied. When the two components were immiscible, the\u0000interfacial tension and isolation free energy were in good agreement, provided\u0000all kinetic and interaction contributions were included in the stress. When the\u0000components were miscible, the values were significantly different. From the\u0000result of PW for the case of completely mixed liquids, the difference was\u0000attributed to the additional free energy required to separate the binary\u0000mixture into single components against the osmotic pressure prior to the\u0000complete detachment of the two components, i.e., the free energy of mixing.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Constructing a self-consistent first-principles framework that accurately predicts the properties of electron transfer reactions through finite-temperature molecular dynamics simulations is a dream of theoretical electrochemists and physical chemists. Yet, predicting even the absolute standard hydrogen electrode potential, the most fundamental reference for electrode potentials, proves to be extremely challenging. Here, we show that a hybrid functional incorporating 25 % exact exchange enables quantitative predictions when statistically accurate phase-space sampling is achieved via thermodynamic integrations and thermodynamic perturbation theory calculations, utilizing machine-learned force fields and $Delta$-machine learning models. The application to seven redox couples, including molecules and transition metal ions, demonstrates that the hybrid functional can predict redox potentials across a wide range of potentials with an average error of 80 mV.
{"title":"Absolute standard hydrogen electrode potential and redox potentials of atoms and molecules: machine learning aided first principles calculations","authors":"Ryosuke Jinnouchi, Ferenc Karsai, Georg Kresse","doi":"arxiv-2409.11000","DOIUrl":"https://doi.org/arxiv-2409.11000","url":null,"abstract":"Constructing a self-consistent first-principles framework that accurately\u0000predicts the properties of electron transfer reactions through\u0000finite-temperature molecular dynamics simulations is a dream of theoretical\u0000electrochemists and physical chemists. Yet, predicting even the absolute\u0000standard hydrogen electrode potential, the most fundamental reference for\u0000electrode potentials, proves to be extremely challenging. Here, we show that a\u0000hybrid functional incorporating 25 % exact exchange enables quantitative\u0000predictions when statistically accurate phase-space sampling is achieved via\u0000thermodynamic integrations and thermodynamic perturbation theory calculations,\u0000utilizing machine-learned force fields and $Delta$-machine learning models.\u0000The application to seven redox couples, including molecules and transition\u0000metal ions, demonstrates that the hybrid functional can predict redox\u0000potentials across a wide range of potentials with an average error of 80 mV.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ana Cobos, Juan Antonio González, Fernando Hevia, Isaías García de la Fuente, Cristina Alonso Tristán
Data on density, $rho$, speed of sound, $c$, and refractive index, $n_{text{D}}$, have been reported at (293-303.15) K for the N,N-dimethylacetamide (DMA) + CH$_3$CO(CH$_2$)$_{u-1}$CH$_3$ ($u$ = 1, 2, 3) systems, and at 298.15 K for the mixture with $u$ = 5. These data have been used to compute excess molar volumes, $V_{text{m}}^{text{E}}$, excess adiabatic compressibilities, $kappa_S^{text{E}}$, and excess speeds of sound $c^{text{E}}$. Negative $V_{text{m}}^{text{E}}$ values indicate the existence of structural effects and interactions between unlike molecules. From excess molar enthalpies, $H_{text{m}}^{text{E}}$, available in the literature for N,N-dimethylformamide (DMF), or N-methylpyrrolidone (NMP) + n-alkanone systems, it is shown: (i) amide-ketone interactions are stronger in DMF systems than in those with NMP; (ii) they become weaker when $u$ increases in mixtures with a given amide. Structural effects largely contribute to $H_{text{m}}^{text{E}}$ and are more relevant in mixtures containing NMP. The application of the Flory's model reveals that the random mixing hypothesis is valid to a large extent for DMF solutions, while NMP systems are characterized by rather strong orientational effects. From values of molar refraction and of the product $P_{text{int}} V_{text{m}}$ (where $P_{text{int}}$ is the internal pressure and $V_{text{m}}$ the molar volume), it is concluded that dispersive interactions increase with $u$, or when DMF is replaced by DMA in mixtures with a fixed ketone.
{"title":"Thermodynamics of amide+ketone mixtures. 2. Volumetric, speed of sound and refractive index data for N,N-dimethylacetamide+2-alkanone systems at several temperatures. Application of Flory's model to tertiary amide+n-alkanone systems","authors":"Ana Cobos, Juan Antonio González, Fernando Hevia, Isaías García de la Fuente, Cristina Alonso Tristán","doi":"arxiv-2409.11309","DOIUrl":"https://doi.org/arxiv-2409.11309","url":null,"abstract":"Data on density, $rho$, speed of sound, $c$, and refractive index,\u0000$n_{text{D}}$, have been reported at (293-303.15) K for the\u0000N,N-dimethylacetamide (DMA) + CH$_3$CO(CH$_2$)$_{u-1}$CH$_3$ ($u$ = 1, 2, 3)\u0000systems, and at 298.15 K for the mixture with $u$ = 5. These data have been\u0000used to compute excess molar volumes, $V_{text{m}}^{text{E}}$, excess\u0000adiabatic compressibilities, $kappa_S^{text{E}}$, and excess speeds of sound\u0000$c^{text{E}}$. Negative $V_{text{m}}^{text{E}}$ values indicate the\u0000existence of structural effects and interactions between unlike molecules. From\u0000excess molar enthalpies, $H_{text{m}}^{text{E}}$, available in the literature\u0000for N,N-dimethylformamide (DMF), or N-methylpyrrolidone (NMP) + n-alkanone\u0000systems, it is shown: (i) amide-ketone interactions are stronger in DMF systems\u0000than in those with NMP; (ii) they become weaker when $u$ increases in mixtures\u0000with a given amide. Structural effects largely contribute to\u0000$H_{text{m}}^{text{E}}$ and are more relevant in mixtures containing NMP. The\u0000application of the Flory's model reveals that the random mixing hypothesis is\u0000valid to a large extent for DMF solutions, while NMP systems are characterized\u0000by rather strong orientational effects. From values of molar refraction and of\u0000the product $P_{text{int}} V_{text{m}}$ (where $P_{text{int}}$ is the\u0000internal pressure and $V_{text{m}}$ the molar volume), it is concluded that\u0000dispersive interactions increase with $u$, or when DMF is replaced by DMA in\u0000mixtures with a fixed ketone.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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