Article
Physics, Multidisciplinary
Ananyo Maitra
Summary: Bulk active fluids are unstable due to activity destroying long-range ordering. However, a 3D active liquid model shows that stable states can form at fluid-fluid interfaces. While active units cannot break rotation symmetry in bulk fluids, they can form stable active nematic and polar states at interfaces. This surface ordering transition may have functional consequences for active transport.
Article
Materials Science, Multidisciplinary
Tuan Khanh Chau, Sung Ju Hong, Haeyong Kang, Dongseok Suh
Summary: The recent discovery of a two-dimensional van der Waals magnet has opened up new possibilities for understanding two-dimensional magnetic systems. By coupling monolayer graphene with the two-dimensional ferromagnet CGT, we are able to electrically monitor the magnetic phase transition of the CGT layer.
NPJ QUANTUM MATERIALS
(2022)
Article
Multidisciplinary Sciences
Srimanta Maity, Garima Arora
Summary: The melting process of two-dimensional Yukawa crystals induced by external perturbations has been explored using molecular dynamics simulations. It is shown that transverse surface waves are generated below a certain threshold value of initial perturbation, but the crystalline order remains. However, above the threshold value, the crystalline order structure breaks and melts. This research provides important insights into the experimental observations of plasma crystals.
SCIENTIFIC REPORTS
(2022)
Article
Materials Science, Multidisciplinary
Ruho Kondo
Summary: In this paper, a method for obtaining two-point direct correlation functions for desired two-dimensional lattices is proposed. The study successfully obtained DCFs for various known and nontrivial lattices through numerical experiments, demonstrating that these lattices can be simulated using a phase-field crystal with at least five modes.
Article
Mathematics, Applied
Yibao Li, Kang Qin, Qing Xia, Junseok Kim
Summary: In this article, a linear, unconditionally energy stable computational scheme is developed to solve the dendritic crystal growth model with the orientational field. The phase field model is applied to describe crystal evolution with rotation. The proposed method is proven to be unconditionally energy stable and preserves second-order spatial and temporal accuracy for numerical approximation. Computational tests show the accuracy, stability, and efficiency of the scheme. (c) 2022 IMACS. Published by Elsevier B.V. All rights reserved.
APPLIED NUMERICAL MATHEMATICS
(2023)
Article
Physics, Fluids & Plasmas
Kedkanok Sitarachu, Michael Bachmann
Summary: In this study, the microcanonical inflection-point analysis method is employed to investigate the phase transitions of the two-dimensional Ising model. The results indicate the existence of higher-order transitions in addition to the second-order ferromagnetic-paramagnetic phase transition. Two independent third-order phase transitions are observed, one in the ferromagnetic phase and the other in the paramagnetic phase.
Article
Mathematics, Applied
Qi Li, Liquan Mei
Summary: This paper examines numerical approximations for two-component PFC models for binary colloidal crystals. By introducing a new type of PFC model and utilizing a stabilized scalar auxiliary variable approach, efficient and stable numerical schemes were developed to accurately simulate phase transformation patterns in 2D and 3D simulations.
JOURNAL OF SCIENTIFIC COMPUTING
(2021)
Article
Chemistry, Physical
Haiqiang Chen, Yutian Lei, Huanhuan Yao, Zhizai Li, Guoqiang Peng, Xufeng Zhou, Haoxu Wang, Qian Wang, Zhiwen Jin
Summary: This study investigates the influence of a binary mixed solvent on the film quality and photovoltaic properties of (PEA)(2)Cs4Pb5I16 (n = 5). It is found that the crystallization rate and crystal growth can be controlled by adjusting the amount of dimethyl sulfoxide (DMSO), leading to improved device performance.
ACS APPLIED ENERGY MATERIALS
(2022)
Article
Chemistry, Applied
Tamar Rosenbaum, Victoria Mbachu, Niall Anthony Mitchell, John Francis Gamble, Patricia Cho, Joshua D. Engstrom
Summary: The 2D population balance model (2D PBM) provides enhanced capability for modeling two different growth kinetics, particularly for needle-like particles in crystallization processes. While the 1D PBM is useful for optimization, it cannot accurately match particle size quantiles or investigate particle aspect ratio changes, highlighting the necessity of the 2D PBM in pharmaceutical industry applications to minimize particle aspect ratio.
ORGANIC PROCESS RESEARCH & DEVELOPMENT
(2022)
Article
Materials Science, Multidisciplinary
Xu Wang, Keyuan Ding, Mengchao Shi, Junhua Li, Bin Chen, Mengjiao Xia, Jie Liu, Yaonan Wang, Jixue Li, En Ma, Ze Zhang, He Tian, Feng Rao
Summary: This study utilizes in situ transmission electron microscopy to investigate the unusual microscopic processes in a Sb2Te3/TiTe2 PCH architecture. The findings reveal that the template-modulated phase transition in this structure is two-dimensional (2D) in nature, with significantly different structural transformation paths and dynamics compared to bulk Sb2Te3. These changes result in suppressed amorphous relaxation and reduced crystallization stochasticity, which are highly advantageous for rapid and precise device operations.
Article
Materials Science, Multidisciplinary
Yuwan Wang, Zichun Cui, Hanghang Zeng, Zijie Wang, Xian Zhang, Junqin Shi, Tengfei Cao, Xiaoli Fan
Summary: The study investigates the intrinsic ferromagnetism of 2D materials based on rare earth metal element GdGe2. Monolayer GdGe2 is found to be a ferromagnetic half-semiconductor with a large magnetic moment and an indirect band gap, while the AB-stacking bilayer GdGe2 shows promise as a high Curie temperature half-metal. Stacking order influences interlayer distance and magnetic coupling of multilayer GdGe2, with potential for modulation of electronic structure and magnetic order through interlayer stacking design.
JOURNAL OF MATERIALS CHEMISTRY C
(2022)
Article
Multidisciplinary Sciences
Qiangsheng Lu, Jacob Cook, Xiaoqian Zhang, Kyle Y. Chen, Matthew Snyder, Duy Tung Nguyen, P. V. Sreenivasa Reddy, Bingchao Qin, Shaoping Zhan, Li-Dong Zhao, Pawel J. Kowalczyk, Simon A. Brown, Tai-Chang Chiang, Shengyuan A. Yang, Tay-Rong Chang, Guang Bian
Summary: Novel 2D Dirac states have been observed in antimony atomic layers with a phosphorene structure. These unpinned Dirac states are located at generic momentum points and can be controlled in momentum space using lattice strains. The dispersions around the unpinned Dirac points are highly anisotropic due to the reduced symmetry of generic momentum points.
NATURE COMMUNICATIONS
(2022)
Article
Engineering, Mechanical
Qinglei Zeng, Manxi Chen, Xiaoqi Yu, Wei Qi, Shengxin Zhu, Heng Yang, Hao-Sen Chen
Summary: Adiabatic shear band (ASB) is an important failure mechanism observed in metals and alloys under impact loading, with a two-dimensional propagating feature. However, in-situ characterization of temperature-deformation fields during ASB formation is challenging due to the small scales involved. In this study, a plane-array infrared imaging system and microspeckle-based digital image correlation technique were used to obtain the two-dimensional features of ASB evolution in titanium alloy specimens. Experimental characterization and simulation results were used to analyze the thermo-mechanical aspects of ASB formation.
INTERNATIONAL JOURNAL OF PLASTICITY
(2023)
Article
Chemistry, Multidisciplinary
Olaya Gomez-Paz, Rosa Carballo, Ana B. Lago, Ezequiel M. Vazquez-Lopez
Summary: Polymorphism is common in crystalline materials but has been little studied in metal organic frameworks. Investigating polymorphism is useful for exploring structure-property relationships, and controlling the synthesis of specific polymorphs can effectively fine-tune the physical properties of materials. In this study, three polymorphs of a copper(i) coordination polymer were prepared and characterized, and their structural and thermal properties were analyzed to understand the differences between the three polymorphic forms.
Article
Chemistry, Physical
Dong Dai, Bobo Cao, Xiao-Lei Hao, Zhi-Hong Li, Zhi-Wu Yu
Summary: Macroscopic scale freestanding 2DCs were discovered in the aqueous dispersions of [Cnmim]X (X = Br, NO3; n = 14, 16, 18) using synchrotron small-and wide-angle X-ray scattering techniques. This unusual phenomenon is attributed to the weak interactions between imidazole headgroups and counterions.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Hossein Vahid, Alberto Scacchi, Xiang Yang, Tapio Ala-Nissila, Maria Sammalkorpi
Summary: In this study, a soft-potential-enhanced Poisson-Boltzmann (SPB) theory was proposed and shown to efficiently capture ion distributions and electrostatic potential around charged macromolecules. The theory was calibrated and compared to particle-based and atomistic simulation models. The results of this study have important implications for understanding the behavior of polyelectrolytes in aqueous salt solutions.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Optics
Fahime Seyedheydari, Kevin Conley, Pasi Yla-Oijala, Ari Sihvola, Tapio Ala-Nissila
Summary: We investigated the electromagnetic response of anisotropic copper antimony disulfide nanoparticles and layers embedded with them. We found that the response strongly depends on the anisotropy and orientation of the nanoparticles. The results demonstrate the potential applications of anisotropic dielectric particles in polarization-dependent-response devices such as solar devices and NIR sensors.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
(2022)
Article
Biochemical Research Methods
Jeta Molla, Alejandro Ponce de Leon Chavez, Takayuki Hiraoka, Tapio Ala-Nissila, Mikko Kivela, Lasse Leskela
Summary: This study compared the effectiveness of heuristic strategies and optimized strategies for COVID-19 vaccine allocation using a mathematical model, finding that simultaneously vaccinating multiple age groups and targeting high-incidence regions can save more lives. It emphasizes the importance of reassessing vaccination strategies at different stages of the epidemic.
PLOS COMPUTATIONAL BIOLOGY
(2022)
Article
Nanoscience & Nanotechnology
V. Vadimov, A. Viitanen, T. Morstedt, T. Ala-Nissila, M. Mottonen
Summary: This study proposes a quantum-circuit refrigerator based on photon-assisted quasiparticle tunneling through a single NIS junction. Compared to previous studies using multiple junctions and an additional charge island, this research directly connects the NIS junction to the electrode of a superconducting microwave resonator, making it immune to low-frequency charge noise. The results show that the bias voltage dependence of QCR-induced damping rate and frequency shift can be reproduced by a semiclassical impedance model for low characteristic impedance resonators.
Correction
Chemistry, Physical
Yanzhou Wang, Zheyong Fan, Ping Qian, Tapio Ala-Nissila, Miguel A. Caro
CHEMISTRY OF MATERIALS
(2022)
Article
Engineering, Civil
Hadi Bordbar, Farid Alinejad, Kevin Conley, Tapio Ala Nissila, Simo Hostikka
Summary: Accurately detecting fires at an early stage is crucial for effective fire prevention and loss reduction, while avoiding false alarms and workplace disruptions. This study takes advantage of recent advances in experimental and numerical methods to simulate the response of a sensor and optimize filter wavelengths for efficient and highly selective flame-radiation-based fire detection sensors.
FIRE SAFETY JOURNAL
(2022)
Article
Chemistry, Physical
Zheyong Fan, Yanzhou Wang, Penghua Ying, Keke Song, Junjie Wang, Yong Wang, Zezhu Zeng, Ke Xu, Eric Lindgren, J. Magnus Rahm, Alexander J. Gabourie, Jiahui Liu, Haikuan Dong, Jianyang Wu, Yue Chen, Zheng Zhong, Jian Sun, Paul Erhart, Yanjing Su, Tapio Ala-Nissila
Summary: We present the latest advancements in machine-learned potentials based on the neuroevolution potential framework and their implementation in the open-source package GPUMD. The accuracy of the models is improved by enhancing the radial and angular descriptors, and their efficient implementation in graphics processing units is described. Comparisons with state-of-the-art MLPs demonstrate the superior accuracy and computational efficiency of the NEP approach. Additionally, an active-learning scheme based on the latent space of a pre-trained NEP model is proposed, and three Python packages are introduced for integrating GPUMD into Python workflows.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Thermodynamics
Penghua Ying, Ting Liang, Ke Xu, Jianbin Xu, Zheyong Fan, Tapio Ala-Nissila, Zheng Zhong
Summary: In this paper, an efficient machine-learned neuroevolution potential model is developed to study the thermal transport in three allotropes of phosphorus. The thermal conductivity values of these allotropes are predicted using molecular dynamics simulations, and the underlying reasons for their significantly different thermal conductivity values are revealed through spectral decomposition, phonon eigenmodes, and phonon participation ratio.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Physics, Multidisciplinary
Hossein Vahid, Alberto Scacchi, Maria Sammalkorpi, Tapio Ala-Nissila
Summary: Multivalent ions in polyelectrolyte solutions cause electrostatic correlations that can alter ion distributions and interactions. Our simulations demonstrate that ion shape and concentration, in addition to valency, can control rigid like-charged polyelectrolyte interactions. We show a correlation between the orientation of aspherical ions and the induced polyelectrolyte attraction through multivalency. This external control over interaction type, strength, and range can guide the self-assembly of like-charged polyelectrolytes.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
K. R. Elder, Zhi-Feng Huang, Tapio Ala-Nissila
Summary: This paper presents a systematic examination of graphene/hexagonal boron nitride (g/hBN) bilayers using a recently developed two-dimensional phase field crystal model that considers out-of-plane deformations. The system parameters are determined by matching the stacking energies and heights of g/hBN bilayers to those obtained from quantum-mechanical density functional theory calculations. The study reveals that out-of-plane deformations reduce the energies of inversion domain boundaries in hBN, and the coupling between graphene and hBN layers results in a bilayer defect configuration consisting of an inversion boundary in hBN and a domain wall in graphene. Simulations of twisted bilayers demonstrate the structure, energy, and elastic properties of moire patterns, and show a transition from well-defined hexagonal network of domain boundaries and junctions to smeared-out patterns as the misorientation angle between the layers increases.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Transportation
Sara Heydari, Zhiren Huang, Takayuki Hiraoka, Alejandro Ponce de Leon Chavez, Tapio Ala-Nissila, Lasse Leskela, Mikko Kivela, Jari Saramaki
Summary: This study investigates the use of multiple data sources, including mobile phones, road traffic sensors, and companies like Google and Facebook, to model mobility patterns and estimate mobility flows in Finland before and during the disruption caused by the COVID-19 pandemic in early 2020. The results show that the model combining past baseline from mobile phone data with up-to-date road traffic data achieves the highest accuracy, followed by radiation and gravity models augmented with traffic data. The findings highlight the usefulness of publicly available road traffic data in mobility modeling and pave the way for a data fusion approach to estimating mobility flows.
TRAVEL BEHAVIOUR AND SOCIETY
(2023)
Article
Physics, Multidisciplinary
Hamidreza Khalilian, Jalal Sarabadani, Tapio Ala-Nissila
Summary: Using Langevin dynamics simulations, we found that the presence of active rods in the environment facilitates the translocation of a flexible linear polymer through a nanopore, even when there are initially more monomers on the cis side. Structural analysis revealed that successful translocation events result in a folded structure of the trans-side subchain induced by the active rods. By varying the rod number density and keeping the initial number of monomers on the cis side subchain fixed, we mapped out a state diagram for successful translocation events, showing a competition between facilitation and crowding.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Physics, Fluids & Plasmas
Xiang Yang, Sahin Buyukdagli, Alberto Scacchi, Maria Sammalkorpi, Tapio Ala-Nissila
Summary: EP mobility reversal refers to the phenomenon where the direction of polymer drift driven by an external electric field is reversed due to the change in sign of the counterion-dressed surface charge. In order to understand this counterintuitive effect, a strong-coupling-dressed Poisson-Boltzmann approach is applied to the cylindrical geometry of the polyelectrolyte-salt system. The derived analytical polymer mobility formula predicts that the increment of monovalent salt, the decrease of multivalent counterion valency, and the increase of the dielectric permittivity of the solvent suppress charge correlations and increase the concentration of multivalent bulk counterions required for EP mobility reversal. Coarse-grained molecular dynamics simulations support these predictions and show the induction of mobility inversion by multivalent counterions at dilute concentrations.
Article
Materials Science, Multidisciplinary
Yanzhou Wang, Zheyong Fan, Ping Qian, Miguel A. Caro, Tapio Ala-Nissila
Summary: In this study, the thermal transport properties of amorphous silicon were systematically investigated using large-scale molecular dynamics simulations. It was found that a simulation cell with up to 64,000 atoms and an appropriate quenching rate are required to achieve almost convergent thermal conductivity. The accuracy of the simulation method was verified by comparing structural properties and experimental results, and the importance of quantum effects in the calculated thermal conductivity was emphasized.
Article
Materials Science, Multidisciplinary
Enzo Granato, K. R. Elder, S. C. Ying, T. Ala-Nissila
Summary: In this study, the effects of thermal fluctuations and pinned boundaries in graphene membranes are investigated using a phasefield crystal model. The height fluctuations in systems with free boundaries exhibit linear diffusion behavior for long times, but still show subdiffusive behavior at intermediate times, consistent with experimental observations. Under compression, mirror buckling fluctuations are found, where the average height changes from above to below the pinned boundaries, and the average time between fluctuations diverges below a critical temperature corresponding to a thermally induced buckling transition. Near the transition, a nonlinear height response is observed, in agreement with recent renormalization group calculations and experimental results on graphene membranes under an external transverse force with clamped boundaries.
