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Considerations in the use of machine learning force fields for free energy calculations. 在自由能计算中使用机器学习力场的考虑。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0252043
Orlando A Mendible-Barreto, Jonathan K Whitmer, Yamil J Colón
{"title":"Considerations in the use of machine learning force fields for free energy calculations.","authors":"Orlando A Mendible-Barreto, Jonathan K Whitmer, Yamil J Colón","doi":"10.1063/5.0252043","DOIUrl":"https://doi.org/10.1063/5.0252043","url":null,"abstract":"<p><p>Machine learning force fields (MLFFs) promise to accurately describe the potential energy surface of molecules at the ab initio level of theory with improved computational efficiency. Within MLFFs, equivariant graph neural networks (EQNNs) have shown great promise in accuracy and performance and are the focus of this work. The capability of EQNNs to recover free energy surfaces (FES) remains to be thoroughly investigated. In this work, we investigate the impact of collective variables (CVs) distribution within the training data on the accuracy of EQNNs predicting the FES of butane and alanine dipeptide. A generalizable workflow is presented in which training configurations are generated with classical molecular dynamics simulations, and energies and forces are obtained with ab initio calculations. We evaluate how bond and angle constraints in the training data influence the accuracy of EQNN force fields in reproducing the FES of the molecules at both classical and ab initio levels of theory. Results indicate that the model's accuracy is unaffected by the distribution of sampled CVs during training, given that the training data includes configurations from characteristic regions of the system's FES. However, when the training data is obtained from classical simulations, the EQNN struggles to extrapolate the free energy for configurations with high free energy. In contrast, models trained with the same configurations on ab initio data show improved extrapolation accuracy. The findings underscore the difficulties in creating a comprehensive training dataset for EQNNs to predict FESs and highlight the importance of prior knowledge of the system's FES.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143966145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Elastic and exchanged atom-molecule collisions in 4He-4He-X (X = 40K, 85Rb, 133Cs) systems at low energy. 低能4He-4He-X (X = 40K, 85Rb, 133c)体系的弹性和交换原子-分子碰撞。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0269552
Huan Zhu, Ning-Ning Gao, Hui-Li Han
{"title":"Elastic and exchanged atom-molecule collisions in 4He-4He-X (X = 40K, 85Rb, 133Cs) systems at low energy.","authors":"Huan Zhu, Ning-Ning Gao, Hui-Li Han","doi":"10.1063/5.0269552","DOIUrl":"https://doi.org/10.1063/5.0269552","url":null,"abstract":"<p><p>We investigate the low-energy collision properties of the 4He-4He-X (X = 40K, 85Rb, 133Cs) systems using the R-matrix propagation method within the hyperspherical coordinate framework. The atom-dimer scattering length and atom-molecule collisional exchange rates are derived by solving the three-body Schrödinger equation using a potential energy surface obtained by summing three realistic pairwise potentials. Our results show that the atom-molecule collision exchange rates in the 4He2 + X → 4HeX + 4He process are primarily governed by the 4HeX two-body scattering lengths. Furthermore, when scaled by this parameter, the inelastic cross sections for all three systems collapse onto a single curve, demonstrating universal behavior. These findings provide new insights into the fundamental properties of weakly bound helium-helium-alkali-metal systems and their role in low-energy three-body collisions.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144009970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
DNA relaxation dynamics in crowded environments: Influence of PEG molecular weight and viscosity. 拥挤环境中的DNA弛豫动力学:PEG分子量和粘度的影响。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0257786
Yunosuke Fuji, Yota Nojiri, Yuuta Moriyama, Toshiyuki Mitsui
{"title":"DNA relaxation dynamics in crowded environments: Influence of PEG molecular weight and viscosity.","authors":"Yunosuke Fuji, Yota Nojiri, Yuuta Moriyama, Toshiyuki Mitsui","doi":"10.1063/5.0257786","DOIUrl":"https://doi.org/10.1063/5.0257786","url":null,"abstract":"<p><p>The coil-globule transition is a key phenomenon in polymer physics, where polymer chains shift between collapsed and extended states. This study investigates the relaxation dynamics of T4 DNA transitioning from an electrohydrodynamically compressed globule to a relaxed coil state in polyethylene glycol (PEG) solutions of varying molecular weights. Using an AC electric field to induce globule formation, we analyzed DNA expansion upon field cessation. Higher molecular weight PEG, particularly PEG 20000, markedly prolonged relaxation times and exhibited broader distributions compared to PEG 4000 and PEG 6000. In PEG 20000, exceeding the overlap concentration stabilized multi-core structures and delayed DNA relaxation. These dynamics diverged from simple exponential relaxation due to persistent entanglements and compressed regions. The findings highlight the significance of crowding effects and viscosity in influencing polymer dynamics, providing insights relevant to biological systems and synthetic applications, such as drug delivery and gene therapy.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144007416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Nonmonotonic concentration dependence of the self-diffusion coefficient of surfactants in wormlike micellar solutions. 蠕虫状胶束溶液中表面活性剂自扩散系数的非单调浓度依赖性。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0266470
Yusuke Koide, Takato Ishida, Takashi Uneyama, Yuichi Masubuchi
{"title":"Nonmonotonic concentration dependence of the self-diffusion coefficient of surfactants in wormlike micellar solutions.","authors":"Yusuke Koide, Takato Ishida, Takashi Uneyama, Yuichi Masubuchi","doi":"10.1063/5.0266470","DOIUrl":"https://doi.org/10.1063/5.0266470","url":null,"abstract":"<p><p>We investigate the concentration dependence of surfactant diffusion in wormlike micellar solutions using dissipative particle dynamics simulations. The simulations show that the self-diffusion coefficient of surfactants exhibits a nonmonotonic dependence on the surfactant concentration, as observed in previous experiments. We quantitatively reveal that this nonmonotonic behavior results from the competition between micellar center-of-mass diffusion and surfactant diffusion within micelles by decomposing the mean-square displacement of surfactants into the corresponding contributions. Furthermore, our detailed analyses demonstrate how the competition between the two diffusion mechanisms is governed by the aggregation number distribution, the dynamics of individual surfactants and micelles, and the kinetics of micellar scission and recombination.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144019814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Superfluidity of quasi-2D 4He droplets on graphite. 石墨上准二维4He液滴的超流动性。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0270881
K M Kolevski, M Boninsegni
{"title":"Superfluidity of quasi-2D 4He droplets on graphite.","authors":"K M Kolevski, M Boninsegni","doi":"10.1063/5.0270881","DOIUrl":"https://doi.org/10.1063/5.0270881","url":null,"abstract":"<p><p>The superfluid response of nanoscale size quasi-2D 4He droplets adsorbed on a graphite substrate is investigated by computer simulations. It is found that clusters comprising as few as 7 atoms are stable at temperatures of ≲0.15 K. Clusters of ∼20 atoms or less are liquid-like and ∼100% superfluid. As the size is increased, the central region crystallizes, forming the commensurate C1/3 phase, with a quasi-1D surface layer of superfluidity possibly evolving into a Luttinger liquid or a transverse quantum superfluid with increasing cluster size. The relevance to quasi-2D molecular spectroscopy is discussed.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144026406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Dynamics of an active chiral polymer in shear flow. 一种活性手性聚合物在剪切流动中的动力学。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0268723
A Gülce Bayram, Luca Biancofiore, Hartmut Löwen
{"title":"Dynamics of an active chiral polymer in shear flow.","authors":"A Gülce Bayram, Luca Biancofiore, Hartmut Löwen","doi":"10.1063/5.0268723","DOIUrl":"https://doi.org/10.1063/5.0268723","url":null,"abstract":"<p><p>We explore the complex formation of an active flexible polymer chain in linear shear flow by using monomer-resolved Brownian dynamics simulations in two spatial dimensions. The chiral head monomer is active and circling, while all other monomers are passive, following both the motion of the head polymer and the shear flow. By the combination of activity, chirality, and shear rate, a wealth of different states are found, including the formation of a linear/complex folding and a spiraling state with both head-in and head-out morphologies. As the vorticity of the applied shear competes with the circling sense of the head, the chirality of the whole complex can be tuned by activity. Our results are relevant to characterize the response of living and artificial chiral active polymer chains to complex flow fields.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144020162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Precision, intelligence, and a new paradigm for chemical research. 精确,智能,化学研究的新范式。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0262187
Shuo Feng, Jun Jiang, Zhenyu Li
{"title":"Precision, intelligence, and a new paradigm for chemical research.","authors":"Shuo Feng, Jun Jiang, Zhenyu Li","doi":"10.1063/5.0262187","DOIUrl":"https://doi.org/10.1063/5.0262187","url":null,"abstract":"<p><p>Chemists have long struggled to precisely regulate and create substances, often relying on trial-and-error methods that are inefficient for complex, high-dimensional research challenges. However, recent advancements in computational and experimental techniques, particularly those with artificial intelligence (AI), are providing new avenues for precision and intelligent chemistry. This perspective highlights the synergistic integration of accurate theoretical simulations, advanced experimental characterization, and AI-driven models, creating a closed-loop system to accelerate chemical discovery and material design. At the core of this framework is an iterative process: precise computational and experimental data lead to advanced intelligent models, which guide the design of optimized reaction parameters or chemical components, and direct robotic platforms that perform reproducible, high-throughput experiments. These experimental data, in turn, provide continuous feedback to refine intelligent models, ultimately enabling precise control of reaction conditions and material properties. To fully realize this vision, we advocate the development of key infrastructures: a multidisciplinary, multimodal, and standardized AI-ready chemical database as a data foundation; a knowledge and logic-enhanced large chemical model for intelligent prediction and design; distributed, full-process robotic laboratories for automated experimentation; and a cloud platform for resource sharing and collaboration. Together, these components constitute a vision for robotic chemist cloud facilities, which will empower researchers with unparalleled capabilities to seamlessly integrate precision and intelligence. This integrated approach promises to accelerate discovery and represents a paradigm shift in chemical research.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144020171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the origin of the breakloose friction force. 关于断裂摩擦力的来源。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0266065
T Tada, B N J Persson
{"title":"On the origin of the breakloose friction force.","authors":"T Tada, B N J Persson","doi":"10.1063/5.0266065","DOIUrl":"https://doi.org/10.1063/5.0266065","url":null,"abstract":"<p><p>We discuss the origin of the static or breakloose friction force and describe a kinetic effect that can manifest itself as an (effective) breakloose friction force. The kinetic effect is important if the kinetic friction force Fk(v) has a maximum at low sliding speed, say for v = vc. If the driving speed v is higher than vc, the friction force at the onset of slip will first increase rapidly to approximately Fk(vc) and then rapidly decrease to Fk(v), resulting in an effective breakloose friction force larger than the kinetic friction force. We present experimental results for sliding friction of a racer rubber tread compound and a passenger car tread compound, which exhibit very different breakloose friction as a result of this kinetic effect. We show that pre-slip in the contact makes the breakloose friction be less than the product of the true contact area and static shear stress. For elastically soft materials, in the absence of the kinetic effect described above, this may result in a breakloose friction force equal to the kinetic friction force. We present experimental results for a passenger car tread compound, which illustrate this effect.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144020436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Analysis of variants of non-adiabatic ring polymer molecular dynamics for calculating excited state dynamics. 计算激发态动力学的非绝热环状聚合物分子动力学变体分析。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0255457
Ziying Cao, Joshua S Kretchmer
{"title":"Analysis of variants of non-adiabatic ring polymer molecular dynamics for calculating excited state dynamics.","authors":"Ziying Cao, Joshua S Kretchmer","doi":"10.1063/5.0255457","DOIUrl":"https://doi.org/10.1063/5.0255457","url":null,"abstract":"<p><p>The non-adiabatic ring polymer molecular dynamics (NRPMD) method, which combines the path-integral ring polymer molecular dynamics framework for the nuclei with the Meyer-Miller-Stock-Thoss mapping of the electronic states, is a powerful tool for simulating non-adiabatic dynamics including nuclear quantum effects. However, challenges arise in utilizing NRPMD associated with zero-point energy leakage between the electronic and nuclear degrees of freedom and ambiguities in how to apply the method under non-equilibrium conditions. Here, we explore several variants of NRPMD and compare their performance using a set of benchmark systems for excited-state electronic population dynamics. Within this context, we adopt an idea from recent work on the linearized semi-classical initial value representation and derive a new NRPMD correlation function for the population of the electronic states in terms of a trace-less operator and the identity operator. The in-depth analysis of the different choices when utilizing NRPMD provides new insight into the practical implementation of the method and related techniques.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144016614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Low energy electron induced fragmentation of hot asparagine and aspartic acid molecules. 低能电子诱导热天冬酰胺和天冬氨酸分子碎裂。
IF 3.1 2区 化学
Journal of Chemical Physics Pub Date : 2025-05-07 DOI: 10.1063/5.0254082
Janina Kopyra, Aleksandr Bancer, Hassan Abdoul-Carime
{"title":"Low energy electron induced fragmentation of hot asparagine and aspartic acid molecules.","authors":"Janina Kopyra, Aleksandr Bancer, Hassan Abdoul-Carime","doi":"10.1063/5.0254082","DOIUrl":"https://doi.org/10.1063/5.0254082","url":null,"abstract":"<p><p>Asparagine (Asn) and aspartic acid (Asp) are not only amino acids found in proteins but also building blocks for synthesis of eco-friendly polymers with techniques such those in which electrons play a role. In this contribution, we present a comparative study of dissociative electron attachment (DEA) to Asn and Asp under gas-phase conditions by means of DEA spectroscopy. In contrast to a number of amino acids studied so far, the formation of the dehydrogenated parent anion, (M - H)-, at about 1.2 eV from both investigated compounds is not the most intense dissociation channel. On the other hand, prominent negative ion resonances are observed peaking below 0.5 eV, resulting in the formation of fragment anions generated from a loss of a neutral -COOH group or neutral H2O2 molecule or leading to the production of HCOO- from both asparagine and aspartic acid. It should be stressed here that the surrogation of one hydroxyl group by an amino group in aspartic acid, which results in the formation of asparagine, sensitizes the latter compound for the loss of an entire neutral carboxyl group. Indeed, the formation of the (Asn - COOH)- anion from DEA to asparagine is more efficient by about an order of magnitude than the formation of the (Asp - COOH)- anion from DEA to aspartic acid.</p>","PeriodicalId":15313,"journal":{"name":"Journal of Chemical Physics","volume":"162 17","pages":""},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144002547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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