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Depletion interaction between cylindrical inclusions in polymer brushes
Authors:
Ji Woong Yu,
Daeseong Yong,
Bae-Yeun Ha,
Changbong Hyeon
Abstract:
Inclusions in mobile brushes experience apparent (depletion) attraction, which arises from a tendency to minimize the volume of depletion zones around the inclusions, thereby to maximize the entropy of the surrounding polymers. Here, we study the brush-induced depletion attraction between cylindrical inclusions using molecular dynamics simulations and the Asakura-Oosawa theory. Our considerations…
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Inclusions in mobile brushes experience apparent (depletion) attraction, which arises from a tendency to minimize the volume of depletion zones around the inclusions, thereby to maximize the entropy of the surrounding polymers. Here, we study the brush-induced depletion attraction between cylindrical inclusions using molecular dynamics simulations and the Asakura-Oosawa theory. Our considerations find that the correlation blobs defined in the brush environment serve as the fundamental units of the attraction. In tall brushes, however, the entropy of the overgrown polymer competes with the depletion attraction between the inclusions. As a result, the brush-induced depletion interaction displays non-monotonic variations with the brush height. Our study not only expands the repertoire of colloid-polymer mixtures to depletion interactions in brushes, but also suggests the brush-induced depletion interaction as a previously unappreciated mechanism for glycocalyx-induced protein cluster formation on cell surfaces.
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Submitted 22 July, 2025; v1 submitted 15 November, 2024;
originally announced November 2024.
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Thermal hysteretic behavior and negative magnetoresistance in an unusual charge-density-wave material EuTe4
Authors:
Q. Q. Zhang,
Y. Shi,
K. Y. Zhai,
W. X. Zhao,
X. Du,
J. S. Zhou,
X. Gu,
R. Z. Xu,
Y. D. Li,
Y. F. Guo,
Z. K. Liu,
C. Chen,
S. -K. Mo,
T. K. Kim,
C. Cacho,
J. W. Yu,
W. Li,
Y. L. Chen,
Jiun-Haw Chu,
L. X. Yang
Abstract:
EuTe4 is a newly-discovered van der Waals material exhibiting a novel charge-density wave (CDW) with a large thermal hysteresis in the resistivity and CDW gap. In this work, we systematically study the electronic structure and transport properties of EuTe4 using high-resolution angle-resolved photoemission spectroscopy (ARPES), magnetoresistance measurements, and scanning tunneling microscopy (STM…
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EuTe4 is a newly-discovered van der Waals material exhibiting a novel charge-density wave (CDW) with a large thermal hysteresis in the resistivity and CDW gap. In this work, we systematically study the electronic structure and transport properties of EuTe4 using high-resolution angle-resolved photoemission spectroscopy (ARPES), magnetoresistance measurements, and scanning tunneling microscopy (STM). We observe a CDW gap of about 200 meV at low temperatures that persists up to 400 K, suggesting that the CDW transition occurs at a much higher temperature. We observe a large thermal hysteretic behavior of the ARPES intensity near the Fermi level, consistent with the resistivity measurement. The hysteresis in the resistivity measurement does not change under a magnetic field up to 7 T, excluding the thermal magnetic hysteresis mechanism. Instead, the surface topography measured with STM shows surface domains with different CDW trimerization directions, which may be important for the thermal hysteretic behavior of EuTe4. Interestingly, we observe a large negative magnetoresistance at low temperatures that can be associated with the canting of magnetically ordered Eu spins. Our work shed light on the understanding of magnetic, transport, and electronic properties of EuTe4.
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Submitted 5 March, 2023;
originally announced March 2023.
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A2I Transformer: Permutation-equivariant attention network for pairwise and many-body interactions with minimal featurization
Authors:
Ji Woong Yu,
Min Young Ha,
Bumjoon Seo,
Won Bo Lee
Abstract:
The combination of neural network potential (NNP) with molecular simulations plays an important role in an efficient and thorough understanding of a molecular system's potential energy surface (PES). However, grasping the interplay between input features and their local contribution to NNP is growingly evasive due to heavy featurization. In this work, we suggest an end-to-end model which directly…
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The combination of neural network potential (NNP) with molecular simulations plays an important role in an efficient and thorough understanding of a molecular system's potential energy surface (PES). However, grasping the interplay between input features and their local contribution to NNP is growingly evasive due to heavy featurization. In this work, we suggest an end-to-end model which directly predicts per-atom energy from the coordinates of particles, avoiding expert-guided featurization of the network input. Employing self-attention as the main workhorse, our model is intrinsically equivariant under the permutation operation, resulting in the invariance of the total potential energy. We tested our model against several challenges in molecular simulation problems, including periodic boundary condition (PBC), $n$-body interaction, and binary composition. Our model yielded stable predictions in all tested systems with errors significantly smaller than the potential energy fluctuation acquired from molecular dynamics simulations. Thus, our work provides a minimal baseline model that encodes complex interactions in a condensed phase system to facilitate the data-driven analysis of physicochemical systems.
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Submitted 27 October, 2021;
originally announced October 2021.
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Active microrheology of a bulk metallic glass
Authors:
Ji Woong Yu,
S. H. E. Rahbari,
Takeshi Kawasaki,
Hyunggyu Park,
Won Bo Lee
Abstract:
The glass transition remains unclarified in condensed matter physics. Investigating the mechanical properties of glass is challenging because any global deformation that may result in shear rejuvenation requires an astronomical relaxation time. Moreover, it is well known that a glass is heterogeneous and a global perturbation cannot explore local mechanical/transport properties. However, an invest…
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The glass transition remains unclarified in condensed matter physics. Investigating the mechanical properties of glass is challenging because any global deformation that may result in shear rejuvenation requires an astronomical relaxation time. Moreover, it is well known that a glass is heterogeneous and a global perturbation cannot explore local mechanical/transport properties. However, an investigation based on a local probe, i.e. microrheology, may overcome these problems. Here, we establish active microrheology of a bulk metallic glass: a probe particle driven into host medium glass. This is a technique amenable for experimental investigations. We show that upon cooling the microscopic friction exhibits a second-order phase transition; this sheds light on the origin of friction in heterogeneous materials. Further, we provide distinct evidence to demonstrate that a strong relationship exists between the microscopic dynamics of the probe particle and the macroscopic properties of the host medium glass. These findings establish active microrheology as a promising technique for investigating the local properties of bulk metallic glass.
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Submitted 5 January, 2020;
originally announced January 2020.