MRSEC Research Data

Persistent link for this collectionhttps://hdl.handle.net/11299/214081

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    Data from: Rapid conformational fluctuations in a model of methylcellulose
    (2017-10-27) Li, Xiaolan; Dorfman, Kevin D; Bates, Frank S; dorfman@umn.edu; Dorfman, Kevin D
    Methylcellulose is a thermoresponsive polymer that undergoes a morphological transition at elevated temperature, forming uniform diameter fibrils. However, the gelation mechanism is still unclear, in particular, at higher polymer concentrations. We use Langevin dynamics simulations to investigate a coarse-grained model for methylcellulose that produces collapsed ringlike structures in dilute solution with a radius close to the fibrils observed in experiments. We show that the competition between the dihedral potential and self-attraction causes these collapsed states to undergo a rapid conformational change, which helps the chain to avoid kinetic traps by permitting a transition between collapsed states. If the dihedral potential is removed, the chains do not escape from their collapsed configuration, whereas at high dihedral potentials, the chains cannot stabilize the collapsed state. We provide systematic data on the effect of the dihedral potential in a model of methylcellulose, and discuss the implication of these previously overlooked rapid conformational fluctuations on the spontaneous formation of high-aspect-ratio fibrils.
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    Resistance vs Temperature of an Indium Oxide thin film sample "6.7E-5" at a range of magnetic fields
    (2019-01-09) Percher, Ilana M; Goldman, Allen M; goldman@umn.edu; Goldman, Allen M; Goldman Group; University of Minnesota Condensed Matter Group
    Sheet resistance of a thin superconducting amorphous indium oxide film as a function of temperature and perpendicular magnetic field. Increasing field leads to the apparent destruction of the superconducting state and a transition to a insulator-like high field state.
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    Input and data for "Simulating precursor steps for fibril formation in methylcellulose solutions"
    (2019-05-08) Sethuraman, Vaidyanathan; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D; Dorfman Research Group
    We use coarse-grained molecular dynamics simulations to study the precursor steps for fibril formation in methylcellulose solutions. Simulations of ring stacking between two collapsed methylcellulose chains demonstrate the existence of a capture radius that is much larger than that predicted by polymer diffusion alone. When two rings are in very close proximity, they stack together to form a fibril precursor. Simulations of stacks of such rings suggest that this structure is metastable. In contrast, chains that are within the capture radius but not in close proximity, as well as for systems containing both ringlike and relaxed chains, fibril-like structures form via a distinctly different mechanism. Irrespective of their initial arrangement, the chains undergo two specific conformational changes: (i) a part of either a ring or a randomly coiled chain splays out and (ii) the splayed chain subsequently engulfs a nearby chain if it is within a certain capture distance. The latter results are consistent with recent experimental measurements of fibril formation by short methylcellulose chains, which suggests the formation of a twisted bundle.
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    Simulation data for "Influence of charge sequence on the adsorption of polyelectrolytes to oppositely-charged polyelectrolyte brushes"
    (2019-06-20) Sethuraman, Vaidyanathan; McGovern, Michael; Morse, David C; Dorfman, Kevin D; vsethura@umn.edu; Sethuraman, Vaidyanathan; Dorfman Group
    When a solution of polyanionic chains is placed in contact with a polycationic brush, the polyanions adsorb into the brush. We investigate the influence of the charge sequences of the free and bound species on the thermodynamics of polyelectrolyte adsorption. As model systems, we consider free and brush polyelectrolytes with either block or alternating charge sequences, and study the adsorption process using coarse-grained Langevin dynamics with implicit solvent, explicit counterions, and excess salt. Free energy, internal energy, and entropy of adsorption are computed using umbrella sampling methods. When the number of polyanions exceed the number of polycations, the brush becomes overcharged. Free chains adsorb most strongly when both free and tethered chains have a block charge sequence, and most weakly when both species have an alternating sequence. Adsorption is stronger when the free polyanion has a block sequence and the tethered polycation is alternating than in the reverse case of an alternating free polymer and a tethered block copolymer. Sequence-dependent effects are shown to be largely energetic, rather than entropic, in origin.
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    High-Resolution Analog of Time-Domain Phonon Spectroscopy in the TEM Experimental Data and Analysis 2019-2020
    (2020-03-16) VandenBussche, Elisah J; Flannigan, David J; flan0076@umn.edu; Flannigan, David J; Flannigan Lab, CEMS Department, University of Minnesota
    The behavior of coherent acoustic phonons (CAPs) as they propagate through a material is a function of the material’s optoelectronic and structural properties, making these collective oscillations a multi-faceted characterization tool. While CAPs are usually detected using transient reflectivity measurements, they have also previously been observed directly in real space using ultrafast electron microscopy (UEM). Here, we report use of UEM to measure localized CAP behavior in an amorphized and annealed GaAs specimen, and demonstrate the sensitivity of this measurement to atomic structure changes. The velocities are compared to expected values for speed of sound in order to draw conclusions about the degree of crystallinity of the specimen pre- and post-annealing. The ability to use a real-space technique to observe CAP behavior with high spatial resolution opens the door to measurements of spatially heterogeneous structural and optoelectronic properties. The data acquired in this experiment as well as analysis code are released here to enable open access to published data.
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    Supporting data for "3D Printed Silicon Nanocrystal Light Emitting Diodes"
    (2020-05-20) Su, Ruitao; Park, Sung Hyun; Li, Zhaohan; McAlpine, Michael C; mcalpine@umn.edu; McAlpine, Michael C; McAlpine Research Group
    The application of 3-D printing to the fabrication of light emitting diode (LED) requires the ability to integrate materials with distinct properties into one functional device by tuning the printability of materials and precisely confining the cured patterns within the predesigned 3-D structure. To meet this goal, material properties, e.g., viscosity, surface tension and degree of crosslinking are optimized to improve the compatibility with the 3-D printing technique. Particularly, silicon nano crystal (SiNC), the nontoxic active material for the printed LED, is investigated in terms of controllable dispensing of the solution-based material as well as surface roughness and uniformity of the printed layer. With the successful red-IR light emission from the printed SiNC-LED, 3-D printing displays the potential to fabricate optoelectronic devices that are flexible, biocompatible and conforming to the surface shape of the target object in a freeform manner.
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    Supporting Data and Codes for Origins of the suppression of fibril formation in grafted methylcellulose solutions
    (2020-05-22) Sethuraman, Vaidyanathan; Dorfman, Kevin D; vsethura@umn.edu; Sethuraman, Vaidyanathan; Dorfman Group
    The data set consists of the codes used to generate and analyze the molecular dynamics trajectories along with the trajectory restart files and the files containing the data points for the figures in the article. It is released for the faithful reproduction of the data in the article.
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    Supporting Data for "From Order to Disorder: Computational Design of Triblock Amphiphiles with 1 nm Domains"
    (2020-07-06) Shen, Zhengyuan; Chen, Jingyi L; Vernadskaia, Viktoriia; Ertem, S Piril; Mahanthappa, Mahesh K; Hillmyer, Marc A; Reineke, Theresa M; Lodge, Timothy P; Siepmann, J Ilja; siepmann@umn.edu; Siepmann, J Ilja; Materials Research Science & Engineering Center (MRSEC)
    Data including input/output and restart files for all the systems, analysis codes (python, fortran, cpp), and figures in the paper "From Order to Disorder: Computational Design of Triblock Amphiphiles with 1 nm Domains." Sample molecular dynamics trajectories pieces are provided due to the extremely long simulation trajectories.
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    Supporting data for Effects of Segment Length Asymmetry in Ternary Diblock Co-polymer-Homopolymer Mixtures
    (2020-07-30) Yadav, Mridul; Morse, David C; Bates, Frank S; yadav051@umn.edu; Yadav, Mridul; Morse Research Group University of Minnesota
    This data set contains data files and scripts to generate results reported in "Effects of Segment Length Asymmetry in Ternary Diblock Copolymer−Homopolymer Mixtures" by Yadav et al. Self-consistent field theory was used to study the effect of asymmetry between A and B statistical segment lengths on interfacial properties and phase behavior in ternary mixtures of AB diblock co-polymers, A homopolymers, and B homopolymers. We consider systems with volumetrically symmetric homopolymers and co-polymer, in which a difference between A and B statistical segment length is the only source of asymmetry between A and B monomers. The sign of the spontaneous curvature of monolayer interfaces between A- and B-rich homopolymer domains is shown to depend on the ratio of co-polymer to homopolymer chain lengths: Interfaces preferentially curve toward the component with a higher statistical segment length when the homopolymer lengths are greater than or comparable to the co- polymer length (as also found in diblock co-polymer melts) but curve away from this component when the homopolymers are much shorter than the co-polymer.
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    Data for "Scattering mechanisms and mobility enhancement in epitaxial BaSnO3thin films probed via electrolyte gating"
    (2020-08-05) Wang, Helin; Prakash, Abhinav; Reich, Konstantin; Ganguly, Koustav; Leighton, Chris; leighton@umn.edu; Leighton, Chris; Leighton Electronic and Magnetism Lab
    Data includes temperature-dependent electronic transport (sheet resistance, electron density, and mobility) of ion-gel-gated BaSnO3 thin films of various thicknesses and growth methods. The mobility vs electron density experimental data and the fitting results (fits) are also provided.
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    Data files of work on LaCoO3 using VASP
    (2020-08-05) Paul, Arpita; Birol, Turan; paula@umn.edu; Paul, Arpita; Birol Research Group
    Sample VASP input file used to study LaCoO3 (INCAR) Band structures of LaCoO3 at each values of strain (used to determine carrier effective mass) Wannier functions derived from e_g orbitals of LaCoO3 (used to determine splitting between dx2-y2 and dz2 orbitals)
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    Suppressing The Ferroelectric Switching Barrier in Hybrid Improper Ferroelectrics
    (2020-08-26) Birol, Turan; Li, Shutong; tbirol@umn.edu; Birol, Turan
    Integration of ferroelectric materials in novel technological applications requires low coercive field materials, and consequently, design strategies to reduce the ferroelectric switching barriers. In this first principles study, we show that biaxial strain, which has a strong e ect on the ferroelectric ground states, can also be used to tune the switching barrier of hybrid improper ferroelectric Ruddlesden-Popper oxides. We identify the region of the strain-tolerance factor phase diagram where this intrinsic barrier is suppressed, and show that it can be explained in relation to strain induced phase transitions to nonpolar phases.
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    Supporting Data for Internal Structure of Methylcellulose Fibrils
    (2020-08-26) Schmidt, Peter W; Morozova, Svetlana; Ertem, S. Piril; Coughlin, McKenzie L; Davidovich, Irina; Talmon, Yeshayahu; Reineke, Theresa M; Bates, Frank S; Lodge, Timothy P; lodge@umn.edu; Lodge, Timothy P; Materials Research Science & Engineering Center (MRSEC)
    Data files used to generate all figures in the manuscript "Internal Structure of Methylcellulose Fibrils" and its supplementary information.
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    Supporting data for spectral rigidity of non-Hermitian symmetric random matrices near the Anderson transition
    (2020-10-27) Shklovskii, Boris, I; Huang, Yi; shklo001@umn.edu; Shklovskii, Boris, I; Materials Research Science & Engineering Center
    We numerically calculate the number variance in the three dimensional TME model and study the evolution of the number variance as a function of average number of eigenvalues with different disorder parameters as the system goes from a metal to an insulator. We use statistics of complex eigenvalues obtained by diagonalization of the TME model on many realizations of cubic lattices with side length L = 8,12,16. The diagonalization is done using LAPACK algorithm. The TME model may be used to describe a random laser.
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    Supporting Data for Mitigating Damage to Hybrid Perovskites Using Pulsed-Beam TEM
    (2021-01-08) VandenBussche, Elisah J; Flannigan, David J; Holmes, Russell J; Clark, Catherine P; vand0837@umn.edu; VandenBussche, Elisah; Flannigan Lab, CEMS Department, University of Minnesota
    Using a pulsed-beam transmission electron microscope, we discover a reduction in damage to methylammonium lead iodide (MAPbI3) as compared to conventional beams delivered at the same dose rates. This work provides insights into damage processes and durability in hybrid perovskites and also illustrates the viability of using pulsed-beam TEM to explore the associated molecular-level routes to degradation, analogous to laser-accelerated energetic pulsed electron beams and the study of damage to biomolecules, cells, and tissues in radiobiology. The data acquired in this experiment are released here to enable open access to published data in accordance with MRSEC data policies.
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    Supporting Data for "Effects of Electrolytes on Thermodynamics and Structure of Oligo(ethylene oxide)/Salt Solutions and Liquid–Liquid Equilibria of a Squalane/Tetraethylene Glycol Dimethyl Ether Blend"
    (2021-01-22) Shen, Zhengyuan; Chen, Qile P; Lodge, Timothy P; Siepmann, J Ilja; siepmann@umn.edu; Siepmann, J Ilja
    Data including input/output and restart files for all the systems, analysis codes (python, fortran, cpp), and figures in the paper "Effects of Electrolytes on Thermodynamics and Structure of Oligo(ethylene oxide)/Salt Solutions and Liquid–Liquid Equilibria of a Squalane/Tetraethylene Glycol Dimethyl Ether Blend". Sample movie files of the production trajectory are provided.
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    Supporting data for Metallic line defect in wide-bandgap transparent perovskite BaSnO₃
    (2021-01-22) Yun, Hwanhui; Topsakal, Mehmet; Prakash, Abhinav; Jalan, Bharat; Jong Seok, Jeong; Birol, Turan; Mkhoyan, K Andre; yunxx133@umn.edu; Yun, Hwanhui
    A line defect with metallic characteristics has been found in optically transparent BaSnO₃ perovskite thin films. The distinct atomic structure of the defect core, composed of Sn and O atoms, was visualized by atomic-resolution scanning transmission electron microscopy (STEM). When doped with La, dopants that replace Ba atoms preferentially segregate to specific crystallographic sites adjacent to the line defect. The electronic structure of the line defect probed in STEM with electron energy-loss spectroscopy was supported by ab initio theory, which indicates the presence of Fermi level–crossing electronic bands that originate from defect core atoms. These metallic line defects also act as electron sinks attracting additional negative charges in these wide-bandgap BaSnO₃ films.
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    Chemical bonding and Born charge in 1T-HfS2
    (2021-04-09) Neal, Sabine N; Li, Shutong; Birol, Turan; Musfeldt, Janice L; li000269@umn.edu; Li, Shutong
    We combine infrared absorption and Raman scattering spectroscopies to explore the properties of 1T-HfS2- a heavy transition metal chalcogenide with strong spin-orbit coupling due to incorporation of the 5d center. We employ the LO-TO splitting of the Eu mode along with a reevaluation of mode mass, unit cell volume, and dielectric constant to reveal the Born effective charge. We find ZB*= 5.33e, in excellent agreement with complementary first principles calculations. In addition to resolving controversy over the nature of chemical bonding in this system, we decompose the Born charge into polarizability and local (ionic) charge. We find α= 5.07 Å3 and Z*= 5.19e, respectively. In order to understand how ZB* relates to the nominal 4+ charge of the Hf center, we decompose the theoretical Born effective charge into band-by-band contributions, and find that polar displacement-induced charge transfer from sulfur p to hafnium d orbitals is responsible for the enhancement of Born charge. 1T-HfS2 is thus an ionic crystal with strong and dynamic covalent effects.
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    Simulation data for "Adsorption of Charge Sequence-Specific Polydisperse Polyelectrolytes"
    (2021-05-28) Sethuraman, Vaidyanathan; Zheng, David; Morse, David C; Dorfman, Kevin D; vsethura@umn.edu; Sethuraman, Vaidyanathan; Dorfman Lab
    Simulation data and codes for reproducing the data in the paper titled "Adsorption of Charge Sequence-Specific Polydisperse Polyelectrolytes".
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    Simulation data from: Free carrier induced ferroelectricity in layered perovskites
    (2021-06-08) Li, Shutong; Birol, Turan; li000269@umn.edu; Li, Shutong
    Doping ferroelectrics with carriers is often detrimental to polarization. This makes the design and discovery of metals that undergo a ferroelectric-like transition challenging. In this letter, we show from first principles that the oxygen octahedral rotations in perovskites are often enhanced by electron doping, and this can be used as a means to strengthen the structural polarization in certain hybrid-improper ferroelectrics -- compounds in which the polarization is not stabilized by the long range Coulomb interactions but is instead induced by a trilinear coupling to octahedral rotations. We use this design strategy to predict a cation ordered Ruddlesden-Popper compound that can be driven into a metallic ferroelectric-like phase via electrolyte gating.