IOP PublishingActa Medica Okayama0021-492262SJ2023Reconfigurable waveguide based on valley topological phononic crystals with local symmetry inversion via continuous translationSJ1002ENMd. ShuzonAliDepartment of Electrical and Electronic Engineering, Okayama UniversityMotokiKataokaDepartment of Electrical and Electronic Engineering, Okayama UniversityMasaakiMisawaDepartment of Electrical and Electronic Engineering, Okayama UniversityKenjiTsurutaDepartment of Electrical and Electronic Engineering, Okayama UniversityWe proposed a reconfigurable valley topological acoustic waveguide constructed using a 2D phononic crystal (PnC) with C3v symmetric arrangement of three rods in the unit cell. An interface between two types of PnCs with differently oriented unit cells exhibits high robustness of the valley transport of acoustic waves via the topologically protected state. Structural reconfiguration was introduced by the continuous translation of rod arrays in the PnCs. The topological phase transition in this translational change was quantitatively identified by the change in the Berry curvature. The translation of the rods leaves a dimer array at the interface, creating a localized/defective mode along the waveguide. Despite the presence of the localized mode, the acoustic wave can propagate along the reconfigurable waveguide the same as the original waveguide. The continuous translation of a rod array can be used to turn on and off the bandgap. This can be a new approach to design a robust acoustic device with a high reconfigurability.No potential conflict of interest relevant to this article was reported.The Japan Society of Vacuum and Surface ScienceActa Medica Okayama1348-03912042022First-principles Analysis of Stearic Acid Adsorption on Calcite (104) Surface261265ENNarumiMachidaGraduate School of Natural Science and Technology, Okayama UniversityMasaakiMisawaFaculty of Natural Science and Technology, Okayama UniversityYukiKezukaShiraishi Central Laboratories Co., Ltd.KenjiTsurutaFaculty of Natural Science and Technology, Okayama UniversityCalcium carbonate nanoparticles are often surface-treated with organic compounds such as fatty acids. The activated calcium carbonates not only exhibit excellent application properties, but also can be applied as eco-friendly inorganic-organic hybrid materials. However, the microscopic adsorption structure of organic compounds on calcite surfaces is not yet well understood. In this study, we performed computational simulations based on density functional theory to investigate adsorption states of stearic acid (SA) on a calcite (104) surface. Based on the first-principles ionic relaxation and molecular dynamics simulations for several types of SA|SA and calcite|SA bonding models, a SA bilayer model on the calcite (104) surface is predicted to be a possible stable structure. The proposed structure model is well consistent with the experimentally predicted adsorption mechanism of SA on the calcite (104) surface.No potential conflict of interest relevant to this article was reported.Nature PortfolioActa Medica Okayama2045-23221212022Defect-free and crystallinity-preserving ductile deformation in semiconducting Ag2S19458ENMasaakiMisawaFaculty of Natural Science and Technology, Okayama UniversityHinataHokyoDepartment of Physics, Kumamoto UniversityShogoFukushimaDepartment of Physics, Kumamoto UniversityKoheiShimamuraDepartment of Physics, Kumamoto UniversityAkihideKouraDepartment of Physics, Kumamoto UniversityFuyukiShimojoDepartment of Physics, Kumamoto UniversityRajiv K.KaliaCollaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, and Department of Biological Science, University of Southern CaliforniaAiichiroNakanoCollaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, and Department of Biological Science, University of Southern CaliforniaPriyaVashishtaCollaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, and Department of Biological Science, University of Southern CaliforniaTypical ductile materials are metals, which deform by the motion of defects like dislocations in association with non-directional metallic bonds. Unfortunately, this textbook mechanism does not operate in most inorganic semiconductors at ambient temperature, thus severely limiting the development of much-needed flexible electronic devices. We found a shear-deformation mechanism in a recently discovered ductile semiconductor, monoclinic-silver sulfide (Ag2S), which is defect-free, omni-directional, and preserving perfect crystallinity. Our first-principles molecular dynamics simulations elucidate the ductile deformation mechanism in monoclinic-Ag2S under six types of shear systems. Planer mass movement of sulfur atoms plays an important role for the remarkable structural recovery of sulfur-sublattice. This in turn arises from a distinctively high symmetry of the anion-sublattice in Ag2S, which is not seen in other brittle silver chalcogenides. Such mechanistic and lattice-symmetric understanding provides a guideline for designing even higher-performance ductile inorganic semiconductors.No potential conflict of interest relevant to this article was reported.MDPIActa Medica Okayama2073-899414102022Design and Robustness Evaluation of Valley Topological Elastic Wave Propagation in a Thin Plate with Phononic Structure2133ENMotokiKataokaDepartment of Electrical and Electronic Engineering, Okayama UniversityMasaakiMisawaDepartment of Electrical and Electronic Engineering, Okayama UniversityKenjiTsurutaDepartment of Electrical and Electronic Engineering, Okayama UniversityBased on the concept of band topology in phonon dispersion, we designed a topological phononic crystal in a thin plate for developing an efficient elastic waveguide. Despite that various topological phononic structures have been actively proposed, a quantitative design strategy of the phononic band and its robustness assessment in an elastic regime are still missing, hampering the realization of topological acoustic devices. We adopted a snowflake-like structure for the crystal unit cell and determined the optimal structure that exhibited the topological phase transition of the planar phononic crystal by changing the unit cell structure. The bandgap width could be adjusted by varying the length of the snow-side branch, and a topological phase transition occurred in the unit cell structure with threefold rotational symmetry. Elastic waveguides based on edge modes appearing at interfaces between crystals with different band topologies were designed, and their transmission efficiencies were evaluated numerically and experimentally. The results demonstrate the robustness of the elastic wave propagation in thin plates. Moreover, we experimentally estimated the backscattering length, which measures the robustness of the topologically protected propagating states against structural inhomogeneities. The results quantitatively indicated that degradation of the immunization against the backscattering occurs predominantly at the corners in the waveguides, indicating that the edge mode observed is a relatively weak topological state.No potential conflict of interest relevant to this article was reported.IOP PublishingActa Medica Okayama0021-492260SD2021Low-frequency sound absorbing metasurface using multilayer split resonatorsSDDA01ENShotaTakasugiDepartment of Electrical and Electronic Engineering, Okayama UniversityKeitaWatanabeDepartment of Electrical and Electronic Engineering, Okayama UniversityMasaakiMisawaDepartment of Electrical and Electronic Engineering, Okayama UniversityKenjiTsurutaDepartment of Electrical and Electronic Engineering, Okayama UniversityAmong the acoustic metasurfaces that can control the propagation of sound waves with the structure far thinner than the wavelength at the operating frequency, the split tube structure has shown its effectiveness in the lower frequency band. Here we focus on multiply layered split tubes to broaden the absorption spectrum. By numerical analysis, we show up-to six-layer structure possessing wideband (1–1000 Hz) sound absorption. The absorbing peaks in the frequency band below 1000 Hz are shown to be multiplexed not only by simple superposition of vibrational modes of each layer, but also by hybridization of the modes indicating collective motion of tubes.No potential conflict of interest relevant to this article was reported.WileyActa Medica Okayama0370-1972257112020First]Principles Study of Pressure]Induced Amorphization of Fe2SiO4 Fayalite2000173ENMasaakiMisawaGraduate School of Natural Science and Technology, Okayama UniversityFuyukiShimojoDepartment of Physics, Kumamoto UniversityFayalite (Fe2SiO4), which is an end member of the olivine series ((FexMg1 | x)2SiO4), undergoes a crystal]to]amorphous transformation under high pressure at room temperature conditions. This pressure]induced amorphized fayalite has an interesting feature: it exhibits antiferromagnetism at low temperature regardless of its non]crystalline structure. In spite of this unique property, the first]principles investigation of pressure]induced amorphized fayalite has not been carried out yet. Herein, to clarify the energetic and structural properties of pressure]induced amorphized fayalite, the first]principles molecular dynamics simulations of the compression and decompression processes of fayalite in the pressure range 0–120 GPa are performed. The energetic and structural properties are also compared with those of well]equilibrated melt]quenched amorphous Fe2SiO4. Based on structural analysis, it is confirmed that not only sixfold but also fivefold coordinated silicon atoms exist in the amorphous]like structure under high pressure. In addition, it is found that the silicon atoms play the role of network former in the amorphous]like phase under high pressure, but change to a network]modifier role after release to ambient conditions. Moreover, it is found that the obtained amorphous]like phase has a partially ordered structure. It is inferred that the partially ordered structure likely enables the pressure]amorphized fayalite to exhibit antiferromagnetism. No potential conflict of interest relevant to this article was reported.American Chemical SocietyActa Medica Okayama1948-718511112020Application of First-Principles-Based Artificial Neural Network Potentials to Multiscale-Shock Dynamics Simulations on Solid Materials45364541ENMasaakiMisawaGraduate School of Natural Science and Technology, Okayama UniversityShogoFukushimaDepartment of Physics, Kumamoto UniversityAkihideKouraDepartment of Physics, Kumamoto UniversityKoheiShimamuraDepartment of Physics, Kumamoto UniversityFuyukiShimojoDepartment of Physics, Kumamoto UniversitySubodhTiwariCollaboratory for Advanced Computing and Simulations, University of Southern CaliforniaKen-ichiNomuraCollaboratory for Advanced Computing and Simulations, University of Southern CaliforniaRajiv K.KaliaCollaboratory for Advanced Computing and Simulations, University of Southern CaliforniaAiichiroNakanoCollaboratory for Advanced Computing and Simulations, University of Southern CaliforniaPriyaVashishtaCollaboratory for Advanced Computing and Simulations, University of Southern CaliforniaThe use of artificial neural network (ANN) potentials trained with first-principles calculations has emerged as a promising approach for molecular dynamics (MD) simulations encompassing large space and time scales while retaining first-principles accuracy. To date, however, the application of ANN-MD has been limited to near-equilibrium processes. Here we combine first-principles-trained ANN-MD with multiscale shock theory (MSST) to successfully describe far-from-equilibrium shock phenomena. Our ANN-MSST-MD approach describes shock-wave propagation in solids with first-principles accuracy but a 5000 times shorter computing time. Accordingly, ANN-MD-MSST was able to resolve fine, long-time elastic deformation at low shock speed, which was impossible with first-principles MD because of the high computational cost. This work thus lays a foundation of ANN-MD simulation to study a wide range of far-from-equilibrium processes.No potential conflict of interest relevant to this article was reported.