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Okushima T, Niiyama T, Ikeda KS, Shimizu Y. Mean first passage times reconstruct the slowest relaxations in potential energy landscapes of nanoclusters. Phys Rev E 2019; 100:032311. [PMID: 31639985 DOI: 10.1103/physreve.100.032311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Indexed: 11/07/2022]
Abstract
Relaxation modes are the collective modes in which all probability deviations from equilibrium states decay with the same relaxation rates. In contrast, a first passage time is the required time for arriving for the first time from one state to another. In this paper, we discuss how and why the slowest relaxation rates of relaxation modes are reconstructed from the first passage times. As an illustrative model, we use a continuous-time Markov state model of vacancy diffusion in KCl nanoclusters. Using this model, we reveal that all characteristics of the relaxations in KCl nanoclusters come from the fact that they are hybrids of two kinetically different regions of the fast surface and slow bulk diffusions. The origin of the different diffusivities turns out to come from the heterogeneity of the activation energies on the potential energy landscapes. We also develop a stationary population method to compute the mean first passage times as mean times required for pair annihilations of particle-hole pairs, which enables us to obtain the symmetric results of relaxation rates under the exchange of the sinks and the sources. With this symmetric method, we finally show why the slowest relaxation times can be reconstructed from the mean first passage times.
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Affiliation(s)
- Teruaki Okushima
- College of Engineering, Chubu University, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan
| | - Tomoaki Niiyama
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-cho, Kanazawa, Ishikawa 920-1192, Japan
| | - Kensuke S Ikeda
- College of Science and Engineering, Ritsumeikan University, Noji-higashi 1-1-1, Kusatsu, shiga 525-8577, Japan
| | - Yasushi Shimizu
- Department of Physics, Ritsumeikan University, Noji-higashi 1-1-1, Kusatsu, shiga 525-8577, Japan
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Okushima T, Niiyama T, Ikeda KS, Shimizu Y. Slowest kinetic modes revealed by metabasin renormalization. Phys Rev E 2018; 97:021301. [PMID: 29548087 DOI: 10.1103/physreve.97.021301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Indexed: 11/07/2022]
Abstract
Understanding the slowest relaxations of complex systems, such as relaxation of glass-forming materials, diffusion in nanoclusters, and folding of biomolecules, is important for physics, chemistry, and biology. For a kinetic system, the relaxation modes are determined by diagonalizing its transition rate matrix. However, for realistic systems of interest, numerical diagonalization, as well as extracting physical understanding from the diagonalization results, is difficult due to the high dimensionality. Here, we develop an alternative and generally applicable method of extracting the long-time scale relaxation dynamics by combining the metabasin analysis of Okushima et al. [Phys. Rev. E 80, 036112 (2009)PLEEE81539-375510.1103/PhysRevE.80.036112] and a Jacobi method. We test the method on an illustrative model of a four-funnel model, for which we obtain a renormalized kinematic equation of much lower dimension sufficient for determining slow relaxation modes precisely. The method is successfully applied to the vacancy transport problem in ionic nanoparticles [Niiyama et al., Chem. Phys. Lett. 654, 52 (2016)CHPLBC0009-261410.1016/j.cplett.2016.04.088], allowing a clear physical interpretation that the final relaxation consists of two successive, characteristic processes.
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Affiliation(s)
- Teruaki Okushima
- Science and Technology Section, General Education Division, College of Engineering, Chubu University, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan
| | - Tomoaki Niiyama
- College of Science and Engineering, Kanazwa University, Kakuma-cho, Kanazawa, Ishikawa 920-1192, Japan
| | - Kensuke S Ikeda
- College of Science and Engineering, Ritsumeikan University, Noji-higashi 1-1-1, Kusatsu 525-8577, Japan
| | - Yasushi Shimizu
- Department of Physics, Ritsumeikan University, Noji-higashi 1-1-1, Kusatsu 525-8577, Japan
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Goswami S, Matula AJ, Rath SP, Hedström S, Saha S, Annamalai M, Sengupta D, Patra A, Ghosh S, Jani H, Sarkar S, Motapothula MR, Nijhuis CA, Martin J, Goswami S, Batista VS, Venkatesan T. Robust resistive memory devices using solution-processable metal-coordinated azo aromatics. NATURE MATERIALS 2017; 16:1216-1224. [PMID: 29058729 DOI: 10.1038/nmat5009] [Citation(s) in RCA: 127] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/15/2017] [Indexed: 06/07/2023]
Abstract
Non-volatile memories will play a decisive role in the next generation of digital technology. Flash memories are currently the key player in the field, yet they fail to meet the commercial demands of scalability and endurance. Resistive memory devices, and in particular memories based on low-cost, solution-processable and chemically tunable organic materials, are promising alternatives explored by the industry. However, to date, they have been lacking the performance and mechanistic understanding required for commercial translation. Here we report a resistive memory device based on a spin-coated active layer of a transition-metal complex, which shows high reproducibility (∼350 devices), fast switching (≤30 ns), excellent endurance (∼1012 cycles), stability (>106 s) and scalability (down to ∼60 nm2). In situ Raman and ultraviolet-visible spectroscopy alongside spectroelectrochemistry and quantum chemical calculations demonstrate that the redox state of the ligands determines the switching states of the device whereas the counterions control the hysteresis. This insight may accelerate the technological deployment of organic resistive memories.
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Affiliation(s)
- Sreetosh Goswami
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456, Singapore
| | - Adam J Matula
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
| | - Santi P Rath
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science (IACS), Jadavpur, Kolkata 700032, India
| | - Svante Hedström
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
| | - Surajit Saha
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - Meenakshi Annamalai
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - Debabrata Sengupta
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science (IACS), Jadavpur, Kolkata 700032, India
| | - Abhijeet Patra
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456, Singapore
| | - Siddhartha Ghosh
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - Hariom Jani
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456, Singapore
| | - Soumya Sarkar
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456, Singapore
| | | | - Christian A Nijhuis
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, Singapore 117546, Singapore
| | - Jens Martin
- Centre for Advanced 2D Materials, National University of Singapore, Singapore 117546, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Sreebrata Goswami
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science (IACS), Jadavpur, Kolkata 700032, India
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
| | - T Venkatesan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
- Materials Science and Engineering Department, National University of Singapore, Singapore 117575, Singapore
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