The Journal of Chemical Physics最新文献_第5页

Fundamental equation of state for mixtures of nitrogen, oxygen, and argon based on molecular simulation data 基于分子模拟数据的氮、氧和氩混合物基本状态方程

The Journal of Chemical Physics Pub Date : 2024-05-01 DOI: 10.1063/5.0188232

Monika Thol, Sven Michael Pohl, Denis Saric, Roland Span, Jadran Vrabec

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Effects of carbon concentration on the local atomic structure of amorphous GST 碳浓度对非晶态 GST 局部原子结构的影响

The Journal of Chemical Physics Pub Date : 2024-05-01 DOI: 10.1063/5.0203532

Robert J. Appleton, Zachary D. McClure, David P. Adams, Alejandro Strachan

{"title":"Effects of carbon concentration on the local atomic structure of amorphous GST","authors":"Robert J. Appleton, Zachary D. McClure, David P. Adams, Alejandro Strachan","doi":"10.1063/5.0203532","DOIUrl":"https://doi.org/10.1063/5.0203532","url":null,"abstract":"Ge-Sb-Te (GST) alloys are leading phase-change materials for data storage due to the fast phase transition between amorphous and crystalline states. Ongoing research aims at improving the stability of the amorphous phase to improve retention. This can be accomplished by the introduction of carbon as a dopant to Ge2Sb2Te5, which is known to alter the short- and mid-range structure of the amorphous phase and form covalently bonded C clusters, both of which hinder crystallization. The relative importance of these processes as a function of C concentration is not known. We used molecular dynamics simulation based on density functional theory to study how carbon doping affects the atomic structure of GST-C. Carbon doping results in an increase in tetrahedral coordination, especially of Ge atoms, and this is known to stabilize the amorphous phase. We observe an unexpected, non-monotonous trend in the number of tetrahedral bonded Ge with the amount of carbon doping. Our simulations show an increase in the number of tetrahedral bonded Ge up to 5 at.% C, after which the number saturates and begins to decrease above 14 at.% C. The carbon atoms aggregate into clusters, mostly in the form of chains and graphene flakes, leaving less carbon to disrupt the GST matrix at higher carbon concentrations. Different degrees of carbon clustering can explain divergent experimental results for recrystallization temperature for carbon doped GST.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837250","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}

引用次数: 0

Bond-selective effect for the dissociative chemisorption of HOD on the Ni(100) surface revealed at the full-dimensional quantum dynamical level 在全维量子动力学水平上揭示 Ni(100) 表面 HOD 离解化学吸附的键选择效应

The Journal of Chemical Physics Pub Date : 2024-05-01 DOI: 10.1063/5.0201925

Tianhui Liu, Bina Fu, Dong H. Zhang

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Exploration of Stokes hydrodynamic law at molecular length scales 探索分子长度尺度上的斯托克斯流体力学定律

The Journal of Chemical Physics Pub Date : 2024-05-01 DOI: 10.1063/5.0203441

Subhajit Acharya, Biman Bagchi

{"title":"Exploration of Stokes hydrodynamic law at molecular length scales","authors":"Subhajit Acharya, Biman Bagchi","doi":"10.1063/5.0203441","DOIUrl":"https://doi.org/10.1063/5.0203441","url":null,"abstract":"The celebrated generalized Stokes law predicts that the velocity of a particle pulled through a liquid by an external force, Fex, is directly proportional to the force and inversely proportional to the friction ζ acted by the medium on the particle. We investigate the range of validity of the generalized Stokes law at molecular length scales by employing computer simulations to calculate friction by pulling a tagged particle with a constant force. We thus calculate friction for two model interaction potentials, Lennard-Jones and soft sphere, for several particle sizes, ranging from radius (a) smaller than the solvent particles to three times larger. We next obtain friction from diffusion (D) by using Einstein’s relation between diffusion and friction ζ in an unperturbed liquid. We find a quantitative agreement between the two at a small-to-intermediate pulling force regime for all the sizes studied. The law does break down at a large pulling force beyond a threshold value. Importantly, the range of validity of Stokes’ scheme to obtain friction increases substantially if we turn off the attractive part of the interaction potential. Additionally, we calculate the viscosity (η) of the unperturbed liquid and find a good agreement with the Stokes–Einstein relation ζ = Cηa for the viscosity dependence with a value of C close to 5 π, which is intermediate between the slip and stick boundary condition.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"107 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140827538","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}

引用次数: 0

Variational umbrella seeding for calculating nucleation barriers 计算成核障碍的变量伞状播种

The Journal of Chemical Physics Pub Date : 2024-05-01 DOI: 10.1063/5.0204540

Willem Gispen, Jorge R. Espinosa, Eduardo Sanz, Carlos Vega, Marjolein Dijkstra

引用次数: 0

Interference is in the eye of the beholder: Application to the coherent control of collisional processes 干扰在观察者眼中：碰撞过程相干控制的应用

The Journal of Chemical Physics Pub Date : 2024-05-01 DOI: 10.1063/5.0202957

Adrien Devolder, Timur V. Tscherbul, Paul Brumer

{"title":"Interference is in the eye of the beholder: Application to the coherent control of collisional processes","authors":"Adrien Devolder, Timur V. Tscherbul, Paul Brumer","doi":"10.1063/5.0202957","DOIUrl":"https://doi.org/10.1063/5.0202957","url":null,"abstract":"Interference is widely regarded as a foundational attribute of quantum mechanics. However, for a given experimental arrangement, interference can either contribute or not contribute to the outcome depending upon the basis in which it is measured. This observation is both foundational and particularly relevant to coherent control of molecular processes, an approach based upon quantum interference. Here, we address this issue and its relevance to controlling molecular processes via the “coherent control scattering (CCS) matrix,” a formalism that allows for an analysis of modifications in an interference structure resulting from a change of basis. This analysis reveals that the change in the interference structure can be attributed to the non-commutativity of the transformation matrix with the CCS matrix and the non-orthogonality of the transformation. Additionally, minimal interference is shown to be associated with the CCS eigenbasis and that the Fourier transform of the eigenvectors of the CCS matrix provides the maximal interference and hence the best coherent control. The change of controllability through a change of basis is illustrated with an example of 85Rb+ 85Rb scattering. In addition, the developed formalism is applied to explain recent experimental results on He + D2 inelastic scattering demonstrating the presence or absence of interference depending on the basis.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140827560","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}

引用次数: 0

Three-phase equilibria of hydrates from computer simulation. I. Finite-size effects in the methane hydrate 计算机模拟的水合物三相平衡。I. 甲烷水合物中的有限尺寸效应

The Journal of Chemical Physics Pub Date : 2024-04-30 DOI: 10.1063/5.0201295

S. Blazquez, J. Algaba, J. M. Míguez, C. Vega, F. J. Blas, M. M. Conde

{"title":"Three-phase equilibria of hydrates from computer simulation. I. Finite-size effects in the methane hydrate","authors":"S. Blazquez, J. Algaba, J. M. Míguez, C. Vega, F. J. Blas, M. M. Conde","doi":"10.1063/5.0201295","DOIUrl":"https://doi.org/10.1063/5.0201295","url":null,"abstract":"Clathrate hydrates are vital in energy research and environmental applications. Understanding their stability is crucial for harnessing their potential. In this work, we employ direct coexistence simulations to study finite-size effects in the determination of the three-phase equilibrium temperature (T3) for methane hydrates. Two popular water models, TIP4P/Ice and TIP4P/2005, are employed, exploring various system sizes by varying the number of molecules in the hydrate, liquid, and gas phases. The results reveal that finite-size effects play a crucial role in determining T3. The study includes nine configurations with varying system sizes, demonstrating that smaller systems, particularly those leading to stoichiometric conditions and bubble formation, may yield inaccurate T3 values. The emergence of methane bubbles within the liquid phase, observed in smaller configurations, significantly influences the behavior of the system and can lead to erroneous temperature estimations. Our findings reveal finite-size effects on the calculation of T3 by direct coexistence simulations and clarify the system size convergence for both models, shedding light on discrepancies found in the literature. The results contribute to a deeper understanding of the phase equilibrium of gas hydrates and offer valuable information for future research in this field.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837371","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}

引用次数: 0

Three-phase equilibria of hydrates from computer simulation. II. Finite-size effects in the carbon dioxide hydrate 计算机模拟的水合物三相平衡。II.二氧化碳水合物中的有限尺寸效应

The Journal of Chemical Physics Pub Date : 2024-04-30 DOI: 10.1063/5.0201306

J. Algaba, S. Blazquez, E. Feria, J. M. Míguez, M. M. Conde, F. J. Blas

{"title":"Three-phase equilibria of hydrates from computer simulation. II. Finite-size effects in the carbon dioxide hydrate","authors":"J. Algaba, S. Blazquez, E. Feria, J. M. Míguez, M. M. Conde, F. J. Blas","doi":"10.1063/5.0201306","DOIUrl":"https://doi.org/10.1063/5.0201306","url":null,"abstract":"In this work, the effects of finite size on the determination of the three-phase coexistence temperature (T3) of the carbon dioxide (CO2) hydrate have been studied by molecular dynamic simulations and using the direct coexistence technique. According to this technique, the three phases involved (hydrate–aqueous solution–liquid CO2) are placed together in the same simulation box. By varying the number of molecules of each phase, it is possible to analyze the effect of simulation size and stoichiometry on the T3 determination. In this work, we have determined the T3 value at 8 different pressures (from 100 to 6000 bar) and using 6 different simulation boxes with different numbers of molecules and sizes. In two of these configurations, the ratio of the number of water and CO2 molecules in the aqueous solution and the liquid CO2 phase is the same as in the hydrate (stoichiometric configuration). In both stoichiometric configurations, the formation of a liquid drop of CO2 in the aqueous phase is observed. This drop, which has a cylindrical geometry, increases the amount of CO2 available in the aqueous solution and can in some cases lead to the crystallization of the hydrate at temperatures above T3, overestimating the T3 value obtained from direct coexistence simulations. The simulation results obtained for the CO2 hydrate confirm the sensitivity of T3 depending on the size and composition of the system, explaining the discrepancies observed in the original work by Míguez et al. [J. Chem Phys. 142, 124505 (2015)]. Non-stoichiometric configurations with larger unit cells show a convergence of T3 values, suggesting that finite-size effects for these system sizes, regardless of drop formation, can be safely neglected. The results obtained in this work highlight that the choice of a correct initial configuration is essential to accurately estimate the three-phase coexistence temperature of hydrates by direct coexistence simulations.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837615","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}

引用次数: 0

Three-phase equilibria of hydrates from computer simulation. III. Effect of dispersive interactions in the methane and carbon dioxide hydrates 计算机模拟的水合物三相平衡。III.甲烷和二氧化碳水合物中分散相互作用的影响

The Journal of Chemical Physics Pub Date : 2024-04-30 DOI: 10.1063/5.0201309

J. Algaba, S. Blazquez, J. M. Míguez, M. M. Conde, F. J. Blas

{"title":"Three-phase equilibria of hydrates from computer simulation. III. Effect of dispersive interactions in the methane and carbon dioxide hydrates","authors":"J. Algaba, S. Blazquez, J. M. Míguez, M. M. Conde, F. J. Blas","doi":"10.1063/5.0201309","DOIUrl":"https://doi.org/10.1063/5.0201309","url":null,"abstract":"In this work, the effect of the range of dispersive interactions in determining the three-phase coexistence line of the CO2 and CH4 hydrates has been studied. In particular, the temperature (T3) at which solid hydrate, water, and liquid CO2/gas CH4 coexist has been determined through molecular dynamics simulations using different cutoff values (from 0.9 to 1.6 nm) for dispersive interactions. The T3 of both hydrates has been determined using the direct coexistence simulation technique. Following this method, the three phases in equilibrium are put together in the same simulation box, the pressure is fixed, and simulations are performed at different temperatures T. If the hydrate melts, then T &gt; T3. Conversely, if the hydrate grows, then T &lt; T3. The effect of the cutoff distance on the dissociation temperature has been analyzed at three different pressures for CO2 hydrate: 100, 400, and 1000 bar. Then, we have changed the guest and studied the effect of the cutoff distance on the dissociation temperature of the CH4 hydrate at 400 bar. Moreover, the effect of long-range corrections for dispersive interactions has been analyzed by running simulations with homo- and inhomogeneous corrections and a cutoff value of 0.9 nm. The results obtained in this work highlight that the cutoff distance for the dispersive interactions affects the stability conditions of these hydrates. This effect is enhanced when the pressure is decreased, displacing the T3 about 2–4 K depending on the system and the pressure.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837253","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}

引用次数: 0

The effect of microsolvation on the structure, nuclear quadrupole coupling, and internal rotation: The methyl carbamate⋯(H2O)1–3 complexes 微溶解对结构、核四极耦合和内旋转的影响：氨基甲酸甲酯⋯(H2O)1-3 复合物

The Journal of Chemical Physics Pub Date : 2024-04-30 DOI: 10.1063/5.0204953

Pablo Pinacho, Juan Carlos López, Zbigniew Kisiel, Susana Blanco

{"title":"The effect of microsolvation on the structure, nuclear quadrupole coupling, and internal rotation: The methyl carbamate⋯(H2O)1–3 complexes","authors":"Pablo Pinacho, Juan Carlos López, Zbigniew Kisiel, Susana Blanco","doi":"10.1063/5.0204953","DOIUrl":"https://doi.org/10.1063/5.0204953","url":null,"abstract":"Microsolvation of the carbamate moiety delivers precise information on complexation effects on the N–C=O backbone and is of relevance to the peptide bond functionality. In this context, the mono-, di-, and trihydrated complexes of methyl carbamate have been studied in molecular expansion by high-resolution microwave spectroscopy, using chirped-pulse and Fabry–Perot resonator Fourier transform microwave instruments covering the frequency range from 2 to 18 GHz. From the rotational constants of the parent and the 18Ow substituted monoisotopologues, accurate values have been derived for the geometries of the hydrogen bond interactions. The nuclear quadrupole coupling constant χcc of the nitrogen nucleus provides a direct measure of complexation changes and decreases with the degree of hydration, whereas the hindered internal rotation barrier increases slightly with microsolvation. Both tendencies could have a common origin in the π-cooperative inductive effects as the microsolvation series progresses. All transitions are split by the internal rotation of the methyl top and the nuclear quadrupole coupling, and in the largest cluster, they are additionally split by an inversion motion.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837366","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}

引用次数: 0