Rodrigo Susial, Ángel Gómez-Hernández, Daniel Lozano-Martín, Dolores del Campo, M. Carmen Martín, José J. Segovia
The development of a novel technique based on a cylindrical microwave resonator for high pressure phase equilibrium determination is described. Electric permittivity or dielectric constant is a physical property that depends on temperature and pressure $epsilon$($p$,$T$). Based on this property, a measuring technique consisting of a cylindrical resonant cavity that works in the microwave spectrum has been developed. Equilibrium data of fluid mixtures are measured at high pressure using a synthetic method, where phase transition is determined under isothermal conditions due to the change of the dielectric constant. This technique may be a more accurate alternative to conventional visual synthetic methods. The technique was validated measuring pure $CO_{2}$, and phase behaviour was then determined for two binary mixtures [$CO_{2}$ (0.6) + $CH_{4}$ (0.4)] and [$CO_{2}$ (0.4) + $CH_{4}$ (0.6)], results for which are presented. These systems are interesting for the study of biogas-like mixtures. In addition, data were compared with the equation of state used for natural gas GERG-2008, and also, they were modelled using Peng-Robinson equation of state and Wong-Sandler mixing rules, which are widely employed in chemical industries and which give good results.
{"title":"A novel technique based on a cylindrical microwave resonator for high pressure phase equilibrium determination","authors":"Rodrigo Susial, Ángel Gómez-Hernández, Daniel Lozano-Martín, Dolores del Campo, M. Carmen Martín, José J. Segovia","doi":"arxiv-2409.08144","DOIUrl":"https://doi.org/arxiv-2409.08144","url":null,"abstract":"The development of a novel technique based on a cylindrical microwave\u0000resonator for high pressure phase equilibrium determination is described.\u0000Electric permittivity or dielectric constant is a physical property that\u0000depends on temperature and pressure $epsilon$($p$,$T$). Based on this\u0000property, a measuring technique consisting of a cylindrical resonant cavity\u0000that works in the microwave spectrum has been developed. Equilibrium data of\u0000fluid mixtures are measured at high pressure using a synthetic method, where\u0000phase transition is determined under isothermal conditions due to the change of\u0000the dielectric constant. This technique may be a more accurate alternative to\u0000conventional visual synthetic methods. The technique was validated measuring\u0000pure $CO_{2}$, and phase behaviour was then determined for two binary mixtures\u0000[$CO_{2}$ (0.6) + $CH_{4}$ (0.4)] and [$CO_{2}$ (0.4) + $CH_{4}$ (0.6)],\u0000results for which are presented. These systems are interesting for the study of\u0000biogas-like mixtures. In addition, data were compared with the equation of\u0000state used for natural gas GERG-2008, and also, they were modelled using\u0000Peng-Robinson equation of state and Wong-Sandler mixing rules, which are widely\u0000employed in chemical industries and which give good results.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190243","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}
Type-I clathrate solids have attracted significant interest due to their ultralow thermal conductivities and subsequent promise for thermoelectric applications, yet the mechanisms underlying these properties are not well understood. Here, we extend the framework of vibrational dynamical mean-field theory (VDMFT) to calculate temperature-dependent thermal transport properties of $X_8$Ga$_{16}$Ge$_{30}$, where $X=$ Ba, Sr, using a many-body Green's function approach. We find that nonresonant scattering between cage acoustic modes and rattling modes leads to a reduction of acoustic phonon lifetimes and thus thermal conductivities. Moreover, we find that the moderate temperature dependence of conductivities above 300 K, which is consistent with experimental measurements, cannot be reproduced by standard perturbation theory calculations, which predict a $T^{-1}$ dependence. Therefore, we conclude that nonperturbative anharmonic effects, including four- and higher-phonon scattering processes, are responsible for the ultralow thermal conductivities of type-I clathrates.
I 型云母状固体因其极低的热导率和热电应用前景而备受关注，然而这些特性的内在机理却不甚明了。在此，我们扩展了振动动力学均场理论（VDMFT）的框架，利用多体格林函数方法计算了 $X_8$Ga$_{16}$Ge$_{30}$ 随温度变化的热传输特性，其中 $X=$ Ba、Sr。我们发现，笼声波模式和响声模式之间的非共振散射导致声波声子寿命和热导率的降低。此外，我们还发现电导率在 300 K 以上的适度温度依赖性与实验测量结果一致，而标准的扰动理论计算却无法再现这种依赖性，因为标准的扰动理论预测电导率与 T^{-1}$ 有关。因此，我们得出结论：非扰动非谐波效应，包括四次和更高的声子散射过程，是造成 I 型氯化物超低热导率的原因。
{"title":"Strong anharmonicity dictates ultralow thermal conductivities of type-I clathrates","authors":"Dipti Jasrasaria, Timothy C. Berkelbach","doi":"arxiv-2409.08242","DOIUrl":"https://doi.org/arxiv-2409.08242","url":null,"abstract":"Type-I clathrate solids have attracted significant interest due to their\u0000ultralow thermal conductivities and subsequent promise for thermoelectric\u0000applications, yet the mechanisms underlying these properties are not well\u0000understood. Here, we extend the framework of vibrational dynamical mean-field\u0000theory (VDMFT) to calculate temperature-dependent thermal transport properties\u0000of $X_8$Ga$_{16}$Ge$_{30}$, where $X=$ Ba, Sr, using a many-body Green's\u0000function approach. We find that nonresonant scattering between cage acoustic\u0000modes and rattling modes leads to a reduction of acoustic phonon lifetimes and\u0000thus thermal conductivities. Moreover, we find that the moderate temperature\u0000dependence of conductivities above 300 K, which is consistent with experimental\u0000measurements, cannot be reproduced by standard perturbation theory\u0000calculations, which predict a $T^{-1}$ dependence. Therefore, we conclude that\u0000nonperturbative anharmonic effects, including four- and higher-phonon\u0000scattering processes, are responsible for the ultralow thermal conductivities\u0000of type-I clathrates.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190245","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}
Understanding the mechanical interplay between silicon anodes and their surrounding solid-electrolyte interphase (SEI) is essential to improve the next generation of lithium-ion batteries. We model and simulate a 2D elliptical silicon nanowire with SEI via a thermodynamically consistent chemo-mechanical continuum ansatz using a higher order finite element method in combination with a variable-step, variable-order time integration scheme. Considering a soft viscoplastic SEI for three half cycles, we see at the minor half-axis the largest stress magnitude at the silicon nanowire surface, leading to a concentration anomaly. This anomaly is caused by the shape of the nanowire itself and not by the SEI. Also for the tangential stress of the SEI, the largest stress magnitudes are at this point, which can lead to SEI fracture. However, for a stiff SEI, the largest stress magnitude inside the nanowire occurs at the major half-axis, causing a reduced concentration distribution in this area. The largest tangential stress of the SEI is still at the minor half-axis. In total, we demonstrate the importance of considering the mechanics of the anode and SEI in silicon anode simulations and encourage further numerical and model improvements.
要改进下一代锂离子电池，就必须了解硅阳极与其周围固态电解质相（SEI）之间的机械相互作用。我们采用高阶有限元法，结合变步变阶时间积分方案，通过热力学一致的化学机械连续反演，对带有 SEI 的二维椭圆硅纳米线进行建模和模拟。考虑到三个半周期的软粘弹性 SEI，我们发现在小半轴处硅纳米线表面的应力最大，从而导致浓度异常。这种异常是由纳米线本身的形状而不是 SEI 引起的。同样，对于 SEI 的切向应力，最大的应力幅度也在这一点上，这可能会导致 SEI 断裂。然而，对于坚硬的 SEI，纳米线内部最大的应力幅度出现在主要半轴处，导致该区域的浓度分布减少。SEI 的最大切向应力仍位于小半轴。总之，我们证明了在硅阳极模拟中考虑阳极和 SEI 力学的重要性，并鼓励进一步改进数值和模型。
{"title":"Elliptical Silicon Nanowire Covered by the SEI in a 2D Chemo-Mechanical Simulation","authors":"Raphael Schoof, Lukas Köbbing, Arnulf Latz, Birger Horstmann, Willy Dörfler","doi":"arxiv-2409.07991","DOIUrl":"https://doi.org/arxiv-2409.07991","url":null,"abstract":"Understanding the mechanical interplay between silicon anodes and their\u0000surrounding solid-electrolyte interphase (SEI) is essential to improve the next\u0000generation of lithium-ion batteries. We model and simulate a 2D elliptical\u0000silicon nanowire with SEI via a thermodynamically consistent chemo-mechanical\u0000continuum ansatz using a higher order finite element method in combination with\u0000a variable-step, variable-order time integration scheme. Considering a soft\u0000viscoplastic SEI for three half cycles, we see at the minor half-axis the\u0000largest stress magnitude at the silicon nanowire surface, leading to a\u0000concentration anomaly. This anomaly is caused by the shape of the nanowire\u0000itself and not by the SEI. Also for the tangential stress of the SEI, the\u0000largest stress magnitudes are at this point, which can lead to SEI fracture.\u0000However, for a stiff SEI, the largest stress magnitude inside the nanowire\u0000occurs at the major half-axis, causing a reduced concentration distribution in\u0000this area. The largest tangential stress of the SEI is still at the minor\u0000half-axis. In total, we demonstrate the importance of considering the mechanics\u0000of the anode and SEI in silicon anode simulations and encourage further\u0000numerical and model improvements.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190247","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 Lozano-Martín, Andres Rojo, M. Carmen Martín, David Vega-Maza, José Juan Segovia
This work aims to provide accurate and wide-ranging experimental new speed of sound data $w$($p$,$T$) of two binary ($CH_{4}$ + $He$) mixtures at a nominal helium content of 5% and 10% at pressures $p$ = (0.5 up to 20) MPa and temperatures $T$ = (273.16, 300, 325, 350 and 375) K. For this purpose, the most accurate technique for determining speed of sound in gas phase has been used: the spherical acoustic resonator. Speed of sound is determined with an overall relative expanded ($k$ = 2) uncertainty of 230 parts in $10^{6}$ and compared to reference models for multicomponent natural gas-like mixtures: AGA8-DC92 and GERG-2008 equations of state. Relative deviations of experimental data from model estimations are outside the experimental uncertainty limit, although all points are mostly within the AGA uncertainty of 0.2% and GERG uncertainty of 0.5% and worsen as the helium content increases. Absolute average deviations are better than 0.45% for GERG and below 0.14% for AGA models in (0.95 $CH_{4}$ + 0.05 $He$) mixture and below 0.83% for GERG and within 0.22% for AGA equations in (0.90 $CH_{4}$ + 0.10 $He$) mixture.
{"title":"Speeds of sound for ($CH_{4}$ + $He$) mixtures from $p$ = (0.5 to 20) MPa at $T$ = (273.16 to 375) K","authors":"Daniel Lozano-Martín, Andres Rojo, M. Carmen Martín, David Vega-Maza, José Juan Segovia","doi":"arxiv-2409.08128","DOIUrl":"https://doi.org/arxiv-2409.08128","url":null,"abstract":"This work aims to provide accurate and wide-ranging experimental new speed of\u0000sound data $w$($p$,$T$) of two binary ($CH_{4}$ + $He$) mixtures at a nominal\u0000helium content of 5% and 10% at pressures $p$ = (0.5 up to 20) MPa and\u0000temperatures $T$ = (273.16, 300, 325, 350 and 375) K. For this purpose, the\u0000most accurate technique for determining speed of sound in gas phase has been\u0000used: the spherical acoustic resonator. Speed of sound is determined with an\u0000overall relative expanded ($k$ = 2) uncertainty of 230 parts in $10^{6}$ and\u0000compared to reference models for multicomponent natural gas-like mixtures:\u0000AGA8-DC92 and GERG-2008 equations of state. Relative deviations of experimental\u0000data from model estimations are outside the experimental uncertainty limit,\u0000although all points are mostly within the AGA uncertainty of 0.2% and GERG\u0000uncertainty of 0.5% and worsen as the helium content increases. Absolute\u0000average deviations are better than 0.45% for GERG and below 0.14% for AGA\u0000models in (0.95 $CH_{4}$ + 0.05 $He$) mixture and below 0.83% for GERG and\u0000within 0.22% for AGA equations in (0.90 $CH_{4}$ + 0.10 $He$) mixture.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190246","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}
Edmund Judge, Mohammed Azzouzi, Austin M. Mroz, Antonio del Rio Chanona, Kim E. Jelfs
Multi fidelity Bayesian optimization (MFBO) leverages experimental and or computational data of varying quality and resource cost to optimize towards desired maxima cost effectively. This approach is particularly attractive for chemical discovery due to MFBO's ability to integrate diverse data sources. Here, we investigate the application of MFBO to accelerate the identification of promising molecules or materials. We specifically analyze the conditions under which lower fidelity data can enhance performance compared to single-fidelity problem formulations. We address two key challenges, selecting the optimal acquisition function, understanding the impact of cost, and data fidelity correlation. We then discuss how to assess the effectiveness of MFBO for chemical discovery.
{"title":"Applying Multi-Fidelity Bayesian Optimization in Chemistry: Open Challenges and Major Considerations","authors":"Edmund Judge, Mohammed Azzouzi, Austin M. Mroz, Antonio del Rio Chanona, Kim E. Jelfs","doi":"arxiv-2409.07190","DOIUrl":"https://doi.org/arxiv-2409.07190","url":null,"abstract":"Multi fidelity Bayesian optimization (MFBO) leverages experimental and or\u0000computational data of varying quality and resource cost to optimize towards\u0000desired maxima cost effectively. This approach is particularly attractive for\u0000chemical discovery due to MFBO's ability to integrate diverse data sources.\u0000Here, we investigate the application of MFBO to accelerate the identification\u0000of promising molecules or materials. We specifically analyze the conditions\u0000under which lower fidelity data can enhance performance compared to\u0000single-fidelity problem formulations. We address two key challenges, selecting\u0000the optimal acquisition function, understanding the impact of cost, and data\u0000fidelity correlation. We then discuss how to assess the effectiveness of MFBO\u0000for chemical discovery.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190254","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}
Sergei V. Kalinin, Eugene A. Eliseev, Anna N. Morozovska
The fundamental aspect of physics of ferroelectric materials is the screening of uncompensated bound charges by the dissociative adsorption of ionic charges from the environment. The adsorption of ions can be especially strong when the ferroelectric undergoes the temperature induced transition from the paraelectric phase to the ferroelectric state. Here we demonstrate that the adsorption of ions and free radicals by the polar surface of ferroelectric nanoparticles can be very efficient in aqueous solutions due to the strong ferro-ionic coupling in the nanoparticles. Obtained results can be useful for the elaboration of alternative methods and tools for adsorption of the cations (Li+, K+, Na+, etc.), anions (Cl-, Br-, J-), and/or free radicals (CO-, NH4+, etc.) from aqueous solutions by the lead-free uniaxial ferroelectric nanoparticles. The results may become an alternative way for the environment-friendly cleaning of different aqueous solutions from ionic contamination as well as for the desalination of sea water using the natural temperature variations.
{"title":"Water Desalination by Ferroelectric Nanoparticles","authors":"Sergei V. Kalinin, Eugene A. Eliseev, Anna N. Morozovska","doi":"arxiv-2409.07318","DOIUrl":"https://doi.org/arxiv-2409.07318","url":null,"abstract":"The fundamental aspect of physics of ferroelectric materials is the screening\u0000of uncompensated bound charges by the dissociative adsorption of ionic charges\u0000from the environment. The adsorption of ions can be especially strong when the\u0000ferroelectric undergoes the temperature induced transition from the\u0000paraelectric phase to the ferroelectric state. Here we demonstrate that the\u0000adsorption of ions and free radicals by the polar surface of ferroelectric\u0000nanoparticles can be very efficient in aqueous solutions due to the strong\u0000ferro-ionic coupling in the nanoparticles. Obtained results can be useful for\u0000the elaboration of alternative methods and tools for adsorption of the cations\u0000(Li+, K+, Na+, etc.), anions (Cl-, Br-, J-), and/or free radicals (CO-, NH4+,\u0000etc.) from aqueous solutions by the lead-free uniaxial ferroelectric\u0000nanoparticles. The results may become an alternative way for the\u0000environment-friendly cleaning of different aqueous solutions from ionic\u0000contamination as well as for the desalination of sea water using the natural\u0000temperature variations.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190252","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}
A central aim of statistical mechanics is to establish connections between a system's microscopic fluctuations and its macroscopic response to a perturbation. For non-equilibrium transport properties, this amounts to establishing Green-Kubo (GK) relationships. In hydrodynamics, relating such GK expressions for liquid-solid friction to macroscopic slip boundary conditions has remained a long-standing problem due to two challenges: (i) The GK running integral of the force autocorrelation function decays to zero rather than reaching a well-defined plateau value; and (ii) debates persist on whether such a transport coefficient measures an intrinsic interfacial friction or an effective friction in the system. Inspired by ideas from the coarse-graining community, we derive a GK relation for liquid-solid friction where the force autocorrelation is sampled with a constraint of momentum conservation in the liquid. Our expression does not suffer from the "plateau problem" and unambiguously measures an effective friction coefficient, in an analogous manner to Stokes' law. We further establish a link between the derived friction coefficient and the hydrodynamic slip length, enabling a straightforward assessment of continuum hydrodynamics across length scales. We find that continuum hydrodynamics describes the simulation results quantitatively for confinement length all the way down to 1 nm. Our results also make clear that water flow under nano-confinement is orders of magnitude slower compared to the macroscopic case. Our approach amounts to a straightforward modification to the present standard method of quantifying interfacial friction from molecular simulations, making possible a sensible comparison between surfaces of vastly different slippage.
{"title":"Flow is slow at the nanoscale: Revisiting the Green-Kubo relation for friction","authors":"Anna T. Bui, Stephen J. Cox","doi":"arxiv-2409.07134","DOIUrl":"https://doi.org/arxiv-2409.07134","url":null,"abstract":"A central aim of statistical mechanics is to establish connections between a\u0000system's microscopic fluctuations and its macroscopic response to a\u0000perturbation. For non-equilibrium transport properties, this amounts to\u0000establishing Green-Kubo (GK) relationships. In hydrodynamics, relating such GK\u0000expressions for liquid-solid friction to macroscopic slip boundary conditions\u0000has remained a long-standing problem due to two challenges: (i) The GK running\u0000integral of the force autocorrelation function decays to zero rather than\u0000reaching a well-defined plateau value; and (ii) debates persist on whether such\u0000a transport coefficient measures an intrinsic interfacial friction or an\u0000effective friction in the system. Inspired by ideas from the coarse-graining\u0000community, we derive a GK relation for liquid-solid friction where the force\u0000autocorrelation is sampled with a constraint of momentum conservation in the\u0000liquid. Our expression does not suffer from the \"plateau problem\" and\u0000unambiguously measures an effective friction coefficient, in an analogous\u0000manner to Stokes' law. We further establish a link between the derived friction\u0000coefficient and the hydrodynamic slip length, enabling a straightforward\u0000assessment of continuum hydrodynamics across length scales. We find that\u0000continuum hydrodynamics describes the simulation results quantitatively for\u0000confinement length all the way down to 1 nm. Our results also make clear that\u0000water flow under nano-confinement is orders of magnitude slower compared to the\u0000macroscopic case. Our approach amounts to a straightforward modification to the\u0000present standard method of quantifying interfacial friction from molecular\u0000simulations, making possible a sensible comparison between surfaces of vastly\u0000different slippage.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224809","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}
The evolution of photosynthetic reaction centers (RCs) from anoxygenic bacteria to oxygenic cyanobacteria and plants reflects their structural and functional adaptation to environmental conditions. Chirality plays a significant role in influencing the arrangement and function of key molecules in these RCs. This study investigates chirality-related energy transfer in two distinct RCs: Thermochromatium tepidum (BRC) and Thermosynechococcus vulcanus (PSII RC) using two-dimensional electronic spectroscopy (2DES). Circularly polarized laser pulses reveal transient chiral dynamics, with 2DCD spectroscopy highlighting chiral contributions. BRC displays more complex chiral behavior, while PSII RC shows faster coherence decay, possibly as an adaptation to oxidative stress. Comparing the chiral dynamics of BRC and PSII RC provides insights into photosynthetic protein evolution and function.
{"title":"Diverse Transient Chiral Dynamics in Evolutionary distinct Photosynthetic Reaction Centers","authors":"Yonglei Yang, Zihui Liu, Fulu Zheng, Panpan Zhang, Hongxing He, Ajay Jha, Hong-Guang Duan","doi":"arxiv-2409.06996","DOIUrl":"https://doi.org/arxiv-2409.06996","url":null,"abstract":"The evolution of photosynthetic reaction centers (RCs) from anoxygenic\u0000bacteria to oxygenic cyanobacteria and plants reflects their structural and\u0000functional adaptation to environmental conditions. Chirality plays a\u0000significant role in influencing the arrangement and function of key molecules\u0000in these RCs. This study investigates chirality-related energy transfer in two\u0000distinct RCs: Thermochromatium tepidum (BRC) and Thermosynechococcus vulcanus\u0000(PSII RC) using two-dimensional electronic spectroscopy (2DES). Circularly\u0000polarized laser pulses reveal transient chiral dynamics, with 2DCD spectroscopy\u0000highlighting chiral contributions. BRC displays more complex chiral behavior,\u0000while PSII RC shows faster coherence decay, possibly as an adaptation to\u0000oxidative stress. Comparing the chiral dynamics of BRC and PSII RC provides\u0000insights into photosynthetic protein evolution and function.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190250","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 Lozano-Martín, María E. Mondéjar, José J. Segovia, César R. Chamorro
Density measurements from single-sinker magnetic suspension densimeters need to be corrected to compensate for the magnetic effects of the measuring cell materials and the fluid on the coupling transmission system. While the magnetic effect of the densimeter materials can be easily determined, the fluid effect requires the calculation of an apparatus-specific constant, $epsilon_{rho}$. In this work, the apparatus-specific constant of the single-sinker magnetic suspension densimeter at the University of Valladolid has been determined by using two alternative methods. The first method, which uses density data for the same fluid and conditions and different sinkers, yielded a value of $epsilon_{rho}$ = $4.6cdot10^{-5}$. The second method, obtained from measurements with pure oxygen, yielded a value of $epsilon_{rho}$ = $8.822cdot10^{-5}$. The second value is considered as more reliable, as the first method presents inherent limitations in this case.
{"title":"Determination of the force transmission error in a single-sinker magnetic suspension densimeter due to the fluid-specific effect and its correction for use with gas mixtures containing oxygen","authors":"Daniel Lozano-Martín, María E. Mondéjar, José J. Segovia, César R. Chamorro","doi":"arxiv-2409.07140","DOIUrl":"https://doi.org/arxiv-2409.07140","url":null,"abstract":"Density measurements from single-sinker magnetic suspension densimeters need\u0000to be corrected to compensate for the magnetic effects of the measuring cell\u0000materials and the fluid on the coupling transmission system. While the magnetic\u0000effect of the densimeter materials can be easily determined, the fluid effect\u0000requires the calculation of an apparatus-specific constant, $epsilon_{rho}$.\u0000In this work, the apparatus-specific constant of the single-sinker magnetic\u0000suspension densimeter at the University of Valladolid has been determined by\u0000using two alternative methods. The first method, which uses density data for\u0000the same fluid and conditions and different sinkers, yielded a value of\u0000$epsilon_{rho}$ = $4.6cdot10^{-5}$. The second method, obtained from\u0000measurements with pure oxygen, yielded a value of $epsilon_{rho}$ =\u0000$8.822cdot10^{-5}$. The second value is considered as more reliable, as the\u0000first method presents inherent limitations in this case.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224808","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}
Rohan Maniar, Priyanka B. Shukla, J. Karl Johnson, Koblar A. Jackson, John P. Perdew
To accurately describe the energetics of transition metal systems, density functional approximations (DFAs) must provide a balanced description of s- and d- electrons. One measure of this is the sd transfer error, which has previously been defined as $E(mathrm{3d}^{n-1} mathrm{4s}^1) -E(mathrm{3d}^{n-2} mathrm{4s}^2)$. Theoretical concerns have been raised on the validity of these results owing to the evaluation of excited-state energies using ground-state DFAs. A more serious concern appears to be strong correlations in the $mathrm{4s}^2$ configuration. Here we define a ground-state measure of the sd transfer error, based on the errors of s- and d-electron second ionization energies of the atoms, that effectively circumvents the aforementioned problems. We find an improved performance as we move from LSDA to PBE to r$^2$SCAN for first-row transition metal atoms. However, we found large (~ 2 eV) ground-state sd transfer errors when applying a Perdew-Zunger self-interaction correction. This is attributed to an "energy penalty" associated with the noded 3d orbitals. A local scaling of the self-interaction correction to LSDA results in a cancellation of s- and d-errors.
为了准确描述过渡金属体系的能量学，密度函数近似（DFA）必须平衡地描述s电子和d电子。其中一个衡量标准是 sd 转移误差，以前的定义是 $E(mathrm{3d}^{n-1}mathrm{4s}^1)-E(mathrm{3d}^{n-2}mathrm{4s}^2)$。由于使用基态 DFA 评估激发态能量，这些结果的有效性引起了理论界的关注。一个更严重的问题似乎是$mathrm{4s}^2$构型中的强相关性。在此，我们根据原子的 s 电子和 d 电子二次电离能的误差，定义了 sd 转移误差的基态测量方法，从而有效地避免了上述问题。我们发现，从 LSDA 到 PBE 再到 r$^2$SCAN，第一排过渡金属原子的性能有所改善。然而，当应用 Perdew-Zunger 自相互作用校正时，我们发现地面状态 sd 转移误差较大（约 2 eV）。这归因于与有节 3d 轨道相关的 "能量惩罚"。对 LSDA 的自作用校正进行局部缩放，可以消除 s 和 d 误差。
{"title":"Ionization energy: sd transfer error and Perdew-Zunger self-interaction correction energy penalty in 3d atoms","authors":"Rohan Maniar, Priyanka B. Shukla, J. Karl Johnson, Koblar A. Jackson, John P. Perdew","doi":"arxiv-2409.07438","DOIUrl":"https://doi.org/arxiv-2409.07438","url":null,"abstract":"To accurately describe the energetics of transition metal systems, density\u0000functional approximations (DFAs) must provide a balanced description of s- and\u0000d- electrons. One measure of this is the sd transfer error, which has\u0000previously been defined as $E(mathrm{3d}^{n-1} mathrm{4s}^1)\u0000-E(mathrm{3d}^{n-2} mathrm{4s}^2)$. Theoretical concerns have been raised on\u0000the validity of these results owing to the evaluation of excited-state energies\u0000using ground-state DFAs. A more serious concern appears to be strong\u0000correlations in the $mathrm{4s}^2$ configuration. Here we define a\u0000ground-state measure of the sd transfer error, based on the errors of s- and\u0000d-electron second ionization energies of the atoms, that effectively\u0000circumvents the aforementioned problems. We find an improved performance as we\u0000move from LSDA to PBE to r$^2$SCAN for first-row transition metal atoms.\u0000However, we found large (~ 2 eV) ground-state sd transfer errors when applying\u0000a Perdew-Zunger self-interaction correction. This is attributed to an \"energy\u0000penalty\" associated with the noded 3d orbitals. A local scaling of the\u0000self-interaction correction to LSDA results in a cancellation of s- and\u0000d-errors.","PeriodicalId":501304,"journal":{"name":"arXiv - PHYS - Chemical Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190248","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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