Samanvitha Sridhar, Ario Khansari, Shaun O’Donnell, Alexandra T. Barth, Evgeny O. Danilov, Felix N. Castellano, Paul A. Maggard, Daniel B. Dougherty
The layered van der Waals material CrCl3 exhibits very strongly bound ligand field excitons that control optoelectronic applications and are connected with magnetic ordering by virtue of their d-orbital origin. Time-resolved photoluminescence of these exciton populations at room temperature shows that their relaxation is dominated by exciton–exciton annihilation and that the spontaneous decay lifetime is very long. These observations allow the rough quantification of the exciton annihilation rate constant and contextualization in light of a recent theory of universal scaling behavior of the annihilation process.
层状范德瓦尔斯材料 CrCl3 显示出非常强的配体场激子束缚，这些激子控制着光电应用，并因其 d 轨道起源而与磁有序性相关联。这些激子群在室温下的时间分辨光致发光表明，它们的弛豫以激子-激子湮灭为主，自发衰变寿命很长。通过这些观察结果，我们可以粗略地量化激子湮灭率常数，并根据湮灭过程的普遍缩放行为的最新理论进行背景分析。
{"title":"Ligand field exciton annihilation in bulk CrCl3","authors":"Samanvitha Sridhar, Ario Khansari, Shaun O’Donnell, Alexandra T. Barth, Evgeny O. Danilov, Felix N. Castellano, Paul A. Maggard, Daniel B. Dougherty","doi":"10.1063/5.0223772","DOIUrl":"https://doi.org/10.1063/5.0223772","url":null,"abstract":"The layered van der Waals material CrCl3 exhibits very strongly bound ligand field excitons that control optoelectronic applications and are connected with magnetic ordering by virtue of their d-orbital origin. Time-resolved photoluminescence of these exciton populations at room temperature shows that their relaxation is dominated by exciton–exciton annihilation and that the spontaneous decay lifetime is very long. These observations allow the rough quantification of the exciton annihilation rate constant and contextualization in light of a recent theory of universal scaling behavior of the annihilation process.","PeriodicalId":501648,"journal":{"name":"The Journal of 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":"142260446","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}
María Victoria Uranga Wassermann, Ezequiel R. Soulé, Cristian Balbuena
This study explores the dynamics of self-assembly and mesophase formation through molecular dynamics simulations of hexagonal and lamellar systems using a simplified coarse-grained model. We focus on characterizing the order–disorder transitions driven by temperature variations and emphasize the often overlooked disordered regime, which serves as a precursor to periodic mesoscale ordering. Our findings not only underscore the morphological richness of the disordered regime, comparable to that of its periodic counterparts, but also reveal the presence of clustering regimes within isotropic phases, thus corroborating prior experimental and theoretical observations. By employing the dynamic correlation coefficient, this work introduces a novel approach to understanding the fundamental mechanisms of mesophase formation, providing new insights into the complex dynamics of self-assembly.
{"title":"From disorder to order: A dynamic approach to mesophase formation in soft sphere model","authors":"María Victoria Uranga Wassermann, Ezequiel R. Soulé, Cristian Balbuena","doi":"10.1063/5.0224154","DOIUrl":"https://doi.org/10.1063/5.0224154","url":null,"abstract":"This study explores the dynamics of self-assembly and mesophase formation through molecular dynamics simulations of hexagonal and lamellar systems using a simplified coarse-grained model. We focus on characterizing the order–disorder transitions driven by temperature variations and emphasize the often overlooked disordered regime, which serves as a precursor to periodic mesoscale ordering. Our findings not only underscore the morphological richness of the disordered regime, comparable to that of its periodic counterparts, but also reveal the presence of clustering regimes within isotropic phases, thus corroborating prior experimental and theoretical observations. By employing the dynamic correlation coefficient, this work introduces a novel approach to understanding the fundamental mechanisms of mesophase formation, providing new insights into the complex dynamics of self-assembly.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260504","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 have recently introduced an original method for sharply partitioning the correlation energy into dynamic and non-dynamic contributions. This method is based on the node of the Hartree–Fock (HF) Slater determinant and the stochastic projector fixed-node diffusion Monte Carlo (FNDMC) method [Šulka et al., J. Chem. Theory Comput. 19, 8147 (2023)]. This approach addresses the challenge of dissecting correlation energy in quantum chemistry. Here, we present the first application of this technique to explore CASSCF correlation energy contributions in selected molecular systems such as BH, FH, F2, and H2–H2. The results show that correlation energies derived from the full-valence active space CASSCF method, often believed to describe mostly non-dynamic correlation effects, contain an extraneous, unwanted, system-dependent component that belongs to the dynamic correlation energy. The findings suggest that the new HF-node/FNDMC-based electron correlation energy decomposition method provides a useful complementary tool, enabling the detection of inherent challenges in distinguishing between dynamic and non-dynamic contributions to correlation energies within methods where precise dissection of these effects is not possible.
{"title":"Unveiling hidden dynamic correlations in CASSCF correlation energies by Hartree–Fock nodes","authors":"Martin Šulka, Katarína Šulková, Matúš Dubecký","doi":"10.1063/5.0223733","DOIUrl":"https://doi.org/10.1063/5.0223733","url":null,"abstract":"We have recently introduced an original method for sharply partitioning the correlation energy into dynamic and non-dynamic contributions. This method is based on the node of the Hartree–Fock (HF) Slater determinant and the stochastic projector fixed-node diffusion Monte Carlo (FNDMC) method [Šulka et al., J. Chem. Theory Comput. 19, 8147 (2023)]. This approach addresses the challenge of dissecting correlation energy in quantum chemistry. Here, we present the first application of this technique to explore CASSCF correlation energy contributions in selected molecular systems such as BH, FH, F2, and H2–H2. The results show that correlation energies derived from the full-valence active space CASSCF method, often believed to describe mostly non-dynamic correlation effects, contain an extraneous, unwanted, system-dependent component that belongs to the dynamic correlation energy. The findings suggest that the new HF-node/FNDMC-based electron correlation energy decomposition method provides a useful complementary tool, enabling the detection of inherent challenges in distinguishing between dynamic and non-dynamic contributions to correlation energies within methods where precise dissection of these effects is not possible.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260507","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 introduce the concept of Kohn–Sham fragment localized molecular orbitals (KS-FLMOs), which are Kohn–Sham molecular orbitals (MOs) localized in specific fragments constituting a generic molecular system. In detail, we minimize the local electronic energies of various fragments, while maximizing the repulsion between them, resulting in the effective localization of the MOs. We use the developed KS-FLMOs to propose a novel energy decomposition analysis, which we name Kohn–Sham fragment energy decomposition analysis, which allows for rationalizing the main non-covalent interactions occurring in interacting systems both in vacuo and in solution, providing physical insights into non-covalent interactions. The method is validated against state-of-the-art energy decomposition analysis techniques and with high-level calculations.
{"title":"Kohn–Sham fragment energy decomposition analysis","authors":"Tommaso Giovannini","doi":"10.1063/5.0216596","DOIUrl":"https://doi.org/10.1063/5.0216596","url":null,"abstract":"We introduce the concept of Kohn–Sham fragment localized molecular orbitals (KS-FLMOs), which are Kohn–Sham molecular orbitals (MOs) localized in specific fragments constituting a generic molecular system. In detail, we minimize the local electronic energies of various fragments, while maximizing the repulsion between them, resulting in the effective localization of the MOs. We use the developed KS-FLMOs to propose a novel energy decomposition analysis, which we name Kohn–Sham fragment energy decomposition analysis, which allows for rationalizing the main non-covalent interactions occurring in interacting systems both in vacuo and in solution, providing physical insights into non-covalent interactions. The method is validated against state-of-the-art energy decomposition analysis techniques and with high-level calculations.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260510","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}
Maria Kelidou, Mohammad Fazelzadeh, Baptiste Parage, Marinde van Dijk, Twan Hooijschuur, Sara Jabbari-Farouji
Self-propelled particles possessing permanent magnetic dipole moments occur naturally in magnetotactic bacteria and can be built into man-made systems such as active colloids or micro-robots. Yet, the interplay between self-propulsion and anisotropic dipole–dipole interactions on dynamic self-assembly in three dimensions (3D) remains poorly understood. We conduct Brownian dynamics simulations of active dipolar particles in 3D, focusing on the low-density regime, where dipolar hard spheres tend to form chain-like aggregates and percolated networks with increasing dipolar coupling strength. We find that strong active forces override dipolar attractions, effectively inhibiting chain-like aggregation and network formation. Conversely, activating particles with low to moderate forces results in a fluid composed of active chains and rings. At strong dipolar coupling strengths, this active fluid transitions into an active gel, consisting of a percolated network of active chains. Although the overall structure of the active gel remains interconnected, the network experiences more frequent configurational rearrangements due to the reduced bond lifetime of active dipolar particles. Consequently, particles exhibit enhanced translational and rotational diffusion within the active fluid of strings and active gels compared to their passive counterparts. We quantify the influence of activity on aggregate topology as they transition from branched structures to unconnected chains and rings. Our findings are summarized in a state diagram, delineating the impact of dipolar coupling strength and active force magnitude on the system.
{"title":"Active string fluids and gels formed by dipolar active Brownian particles in 3D","authors":"Maria Kelidou, Mohammad Fazelzadeh, Baptiste Parage, Marinde van Dijk, Twan Hooijschuur, Sara Jabbari-Farouji","doi":"10.1063/5.0215545","DOIUrl":"https://doi.org/10.1063/5.0215545","url":null,"abstract":"Self-propelled particles possessing permanent magnetic dipole moments occur naturally in magnetotactic bacteria and can be built into man-made systems such as active colloids or micro-robots. Yet, the interplay between self-propulsion and anisotropic dipole–dipole interactions on dynamic self-assembly in three dimensions (3D) remains poorly understood. We conduct Brownian dynamics simulations of active dipolar particles in 3D, focusing on the low-density regime, where dipolar hard spheres tend to form chain-like aggregates and percolated networks with increasing dipolar coupling strength. We find that strong active forces override dipolar attractions, effectively inhibiting chain-like aggregation and network formation. Conversely, activating particles with low to moderate forces results in a fluid composed of active chains and rings. At strong dipolar coupling strengths, this active fluid transitions into an active gel, consisting of a percolated network of active chains. Although the overall structure of the active gel remains interconnected, the network experiences more frequent configurational rearrangements due to the reduced bond lifetime of active dipolar particles. Consequently, particles exhibit enhanced translational and rotational diffusion within the active fluid of strings and active gels compared to their passive counterparts. We quantify the influence of activity on aggregate topology as they transition from branched structures to unconnected chains and rings. Our findings are summarized in a state diagram, delineating the impact of dipolar coupling strength and active force magnitude on the system.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"207 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260512","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 derive an analytic expression of the non-equilibrium Fermi’s golden rule (NE-FGR) expression for a Holstein–Tavis–Cumming Hamiltonian, a universal model for many molecules collectively coupled to the optical cavity. These NE-FGR expressions capture the full-time-dependent behavior of the rate constant for transitions from polariton states to dark states. The rate is shown to be reduced to the well-known frequency domain-based equilibrium Fermi’s golden rule (E-FGR) expression in the equilibrium and collective limit and is shown to retain the same scaling with the number of sites in non-equilibrium and non-collective cases. We use these NE-FGR to perform population dynamics with a time-non-local and time-local quantum master equation and obtain accurate population dynamics from the initially occupied upper or lower polariton states. Furthermore, NE-FGR significantly improves the accuracy of the population dynamics when starting from the lower polariton compared to the E-FGR theory, highlighting the importance of the non-Markovian behavior and the short-time transient behavior in the transition rate constant.
{"title":"Non-equilibrium rate theory for polariton relaxation dynamics","authors":"Yifan Lai, Wenxiang Ying, Pengfei Huo","doi":"10.1063/5.0231396","DOIUrl":"https://doi.org/10.1063/5.0231396","url":null,"abstract":"We derive an analytic expression of the non-equilibrium Fermi’s golden rule (NE-FGR) expression for a Holstein–Tavis–Cumming Hamiltonian, a universal model for many molecules collectively coupled to the optical cavity. These NE-FGR expressions capture the full-time-dependent behavior of the rate constant for transitions from polariton states to dark states. The rate is shown to be reduced to the well-known frequency domain-based equilibrium Fermi’s golden rule (E-FGR) expression in the equilibrium and collective limit and is shown to retain the same scaling with the number of sites in non-equilibrium and non-collective cases. We use these NE-FGR to perform population dynamics with a time-non-local and time-local quantum master equation and obtain accurate population dynamics from the initially occupied upper or lower polariton states. Furthermore, NE-FGR significantly improves the accuracy of the population dynamics when starting from the lower polariton compared to the E-FGR theory, highlighting the importance of the non-Markovian behavior and the short-time transient behavior in the transition rate constant.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260514","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}
Zhilong Zhang, Rong Wu, Jianyong Yue, YaLi Zhu, JiaLei Hui
In this work, a hollow MoSe2/CuS type-II heterojunction was fabricated using hollow MoSe2 nanospheres as the basis for structural design. UV–Vis–NIR diffuse absorption tests show that MoSe2/CuS has a broad spectral absorption to extend the optical response range from UV–Vis to NIR. The light source utilization rate and interfacial area are increased by the hollow MoSe2/CuS core–shell structure. The broad absorption ability of MoSe2/CuS can facilitate the photocatalysis process. As the electrochemical impedance of MoSe2/CuS is lower than that of the MoSe2, MoSe2/CuS has a good photogenerated carrier separation efficiency. Benefiting from the synergistic facilitation effect of the multi-level 3D hollow nanosphere and the significant space charge region in type-II heterojunction, the RhB degradation efficiency of MoSe2/CuS reached 96.0% in 120.0 min under Xe (350 W) broadband spectrum light irradiation. The photocatalysis mechanism of the hollow MoSe2/CuS core–shell structure was investigated. This work provides an insight into the application of broad spectrum semiconductor heterojunctions to solve environmental problems.
在这项工作中，以空心 MoSe2 纳米球为结构设计基础，制备了空心 MoSe2/CuS II 型异质结。紫外-可见-近红外扩散吸收测试表明，MoSe2/CuS 具有宽光谱吸收特性，可将光响应范围从紫外-可见光扩展到近红外。中空的 MoSe2/CuS 核壳结构提高了光源利用率和界面面积。MoSe2/CuS 的宽吸收能力可促进光催化过程。由于 MoSe2/CuS 的电化学阻抗低于 MoSe2，因此 MoSe2/CuS 具有良好的光生载流子分离效率。得益于多级三维中空纳米球的协同促进效应和 II 型异质结中显著的空间电荷区，MoSe2/CuS 在 Xe（350 W）宽带光谱光照射下，120.0 min 内的 RhB 降解效率达到 96.0%。研究了中空 MoSe2/CuS 核壳结构的光催化机理。这项研究为应用宽光谱半导体异质结解决环境问题提供了新的视角。
{"title":"Designing a hollow MoSe2/CuS nanospheres type-II heterojunction photocatalyst with superior UV–vis-NIR absorption for photocatalytic degradation of organic pollutants","authors":"Zhilong Zhang, Rong Wu, Jianyong Yue, YaLi Zhu, JiaLei Hui","doi":"10.1063/5.0209430","DOIUrl":"https://doi.org/10.1063/5.0209430","url":null,"abstract":"In this work, a hollow MoSe2/CuS type-II heterojunction was fabricated using hollow MoSe2 nanospheres as the basis for structural design. UV–Vis–NIR diffuse absorption tests show that MoSe2/CuS has a broad spectral absorption to extend the optical response range from UV–Vis to NIR. The light source utilization rate and interfacial area are increased by the hollow MoSe2/CuS core–shell structure. The broad absorption ability of MoSe2/CuS can facilitate the photocatalysis process. As the electrochemical impedance of MoSe2/CuS is lower than that of the MoSe2, MoSe2/CuS has a good photogenerated carrier separation efficiency. Benefiting from the synergistic facilitation effect of the multi-level 3D hollow nanosphere and the significant space charge region in type-II heterojunction, the RhB degradation efficiency of MoSe2/CuS reached 96.0% in 120.0 min under Xe (350 W) broadband spectrum light irradiation. The photocatalysis mechanism of the hollow MoSe2/CuS core–shell structure was investigated. This work provides an insight into the application of broad spectrum semiconductor heterojunctions to solve environmental problems.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260508","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}
When encountering complex fluorescence decays that deviate from exponentiality, a very appealing approach is to use lifetime or rate constant distributions. These are related by Laplace transform to the sum of exponential functions, stretched exponentials, Becquerel’s decay function, and others. However, the limitations of this approach have not been sufficiently discussed in the literature. In particular, the time-independent probability distributions of the rate constants or decay times are occasionally used to describe bimolecular quenching. We show that in such a case, this mathematical formalism has a clear physical interpretation only when the fluorophore and quencher molecules are immobile, as in the solid state. However, such an interpretation is no longer possible once we consider the motion of fluorophores with respect to quenchers. Therefore, for systems in which the relative motion of fluorophores and quenchers cannot be neglected, it is not appropriate to use the time-independent rate or decay time distributions to describe, fit, or rationalize experimental results on fluorescence decay.
{"title":"Limitations of the rate-distribution formalism in describing luminescence quenching in the presence of diffusion","authors":"Jakub Jędrak, Gonzalo Angulo","doi":"10.1063/5.0223438","DOIUrl":"https://doi.org/10.1063/5.0223438","url":null,"abstract":"When encountering complex fluorescence decays that deviate from exponentiality, a very appealing approach is to use lifetime or rate constant distributions. These are related by Laplace transform to the sum of exponential functions, stretched exponentials, Becquerel’s decay function, and others. However, the limitations of this approach have not been sufficiently discussed in the literature. In particular, the time-independent probability distributions of the rate constants or decay times are occasionally used to describe bimolecular quenching. We show that in such a case, this mathematical formalism has a clear physical interpretation only when the fluorophore and quencher molecules are immobile, as in the solid state. However, such an interpretation is no longer possible once we consider the motion of fluorophores with respect to quenchers. Therefore, for systems in which the relative motion of fluorophores and quenchers cannot be neglected, it is not appropriate to use the time-independent rate or decay time distributions to describe, fit, or rationalize experimental results on fluorescence decay.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260511","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}
Haimi Nguyen, Nathan Ng, Lachlan P. Lindoy, Gunhee Park, Andrew J. Millis, Garnet Kin-Lic Chan, David R. Reichman
We investigate the application of matrix product state (MPS) representations of the influence functionals (IFs) for the calculation of real-time equilibrium correlation functions in open quantum systems. Focusing specifically on the unbiased spin-boson model, we explore the use of IF-MPSs for complex time propagation, as well as IF-MPSs for constructing correlation functions in the steady state. We examine three different IF approaches: one based on the Kadanoff–Baym contour targeting correlation functions at all times, one based on a complex contour targeting the correlation function at a single time, and a steady state formulation, which avoids imaginary or complex times, while providing access to correlation functions at all times. We show that within the IF language, the steady state formulation provides a powerful approach to evaluate equilibrium correlation functions.
我们研究了影响函数（IFs）的矩阵乘积状态（MPS）表示法在计算开放量子系统的实时平衡相关函数中的应用。我们特别关注无偏自旋玻色子模型，探索如何使用 IF-MPS 进行复杂时间传播，以及如何使用 IF-MPS 构建稳态相关函数。我们研究了三种不同的 IF 方法：一种基于 Kadanoff-Baym 等值线，以所有时间的相关函数为目标；一种基于复杂等值线，以单个时间的相关函数为目标；还有一种稳态表述，避免虚时间或复杂时间，同时提供所有时间的相关函数。我们表明，在 IF 语言中，稳态表述为评估平衡相关函数提供了一种强大的方法。
{"title":"Correlation functions from tensor network influence functionals: The case of the spin-boson model","authors":"Haimi Nguyen, Nathan Ng, Lachlan P. Lindoy, Gunhee Park, Andrew J. Millis, Garnet Kin-Lic Chan, David R. Reichman","doi":"10.1063/5.0224880","DOIUrl":"https://doi.org/10.1063/5.0224880","url":null,"abstract":"We investigate the application of matrix product state (MPS) representations of the influence functionals (IFs) for the calculation of real-time equilibrium correlation functions in open quantum systems. Focusing specifically on the unbiased spin-boson model, we explore the use of IF-MPSs for complex time propagation, as well as IF-MPSs for constructing correlation functions in the steady state. We examine three different IF approaches: one based on the Kadanoff–Baym contour targeting correlation functions at all times, one based on a complex contour targeting the correlation function at a single time, and a steady state formulation, which avoids imaginary or complex times, while providing access to correlation functions at all times. We show that within the IF language, the steady state formulation provides a powerful approach to evaluate equilibrium correlation functions.","PeriodicalId":501648,"journal":{"name":"The Journal of Chemical Physics","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260509","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}
Polyampholytes (PAs) are charged polymers composed of positively and negatively charged monomers along their backbone. The sequence of the charged monomers and the bending of the chain significantly influence the conformation and dynamical behavior of the PA. Using coarse-grained molecular dynamics simulations, we comprehensively study the structural and dynamical properties of flexible and semi-flexible PAs. The simulation results demonstrate a flexible PA chain, displaying a transition from a coil to a globule in the parameter space of the charge sequence. In addition, the behavior of the mean-square displacement (MSD), denoted as ⟨(Δr(t))2⟩, reveals distinct dynamics, specifically for the alternating and charge-segregated sequences. The MSD follows a power-law behavior, where ⟨(Δr(t))2⟩ ∼ tβ, with β ≈ 3/5 and β ≈ 1/2 for the alternating sequence and the charge-segregated sequence in the absence of hydrodynamic interactions, respectively. However, when hydrodynamic interactions are incorporated, the exponent β shifts to ∼3/5 for the charge-segregated sequence and 2/3 for the well-mixed alternating sequence. For a semi-flexible PA chain, varying the bending rigidity and electrostatic interaction strength (Γe) leads to distinct, fascinating conformational states, including globule, bundle, and torus-like conformations. We show that PAs acquire circular and hairpin-like conformations in the intermediate bending regime. The transition between various conformations is identified in terms of the shape factor estimated from the ratios of eigenvalues of the gyration tensor.
聚阴离子（PA）是由带正电和负电的单体沿主干组成的带电聚合物。带电单体的序列和链的弯曲对 PA 的构象和动力学行为有重大影响。利用粗粒度分子动力学模拟，我们全面研究了柔性和半柔性 PA 的结构和动力学特性。模拟结果表明，柔性 PA 链在电荷序列的参数空间中显示出从线圈到球状的过渡。此外，均方位移（MSD）（表示为⟨(Δr(t))2⟩）的行为揭示了不同的动态，特别是交替序列和电荷分离序列。MSD 遵循幂律行为，其中⟨(Δr(t))2⟩∼tβ，在没有流体动力学相互作用的情况下，交替序列和电荷隔离序列分别为 β≈ 3/5 和 β≈ 1/2。然而，当加入流体动力学相互作用时，电荷隔离序列的指数 β 变为 ∼3/5，混合良好的交替序列的指数 β 变为 2/3。对于半柔性 PA 链，改变弯曲刚度和静电相互作用强度（Γe）会导致不同的迷人构象状态，包括球状、束状和环状构象。我们的研究表明，在中间弯曲机制下，PA 可获得环状和发夹状构象。根据回旋张量特征值的比率估算出的形状因子确定了各种构象之间的转变。
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