Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y02: Liquids, Glasses and CrystalsRecordings Available
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Chair: Safura Sharifi, University of Illinois at Urbana-Champai Room: McCormick Place W-175C |
Friday, March 18, 2022 8:00AM - 8:12AM |
Y02.00001: Liquid-Liquid Criticality from First Principles in a Flexible Model of Water John Weis, Athanassios Panagiotopoulos, Francesco Sciortino, Pablo G Debenedetti A metastable liquid-liquid critical point is demonstrated and rigorously located under deeply supercooled conditions in the WAIL model of water, a classical force field parameterized using only ab initio data only as opposed to specific thermophysical properties. The hypothesis that the anomalous behavior of liquid water is related to the existence of a second critical point in deeply supercooled states has long been the subject of intense debate. Recent experimental results and simulations studies based on rigid classical models parameterized to reproduce thermodynamic properties of water have provided support to this hypothesis. The WAIL model incorporates several novel features: it is both flexible and polarizable, properties which can significantly influence the phase behavior of water. The relationship between the second critical point and the two distinct liquids which form in deeply supercooled states with water thermodynamic anomalies is confirmed by the present study in which the water-water phase separation is predicted using only ab-initio calculations. The manner in which the presence of two distinct but interconvertible structures give rise to the well-known thermophysical anomalies of deeply supercooled water is also shown empirically. |
Friday, March 18, 2022 8:12AM - 8:24AM |
Y02.00002: Hydrodynamics and Mesoscopic Liquid Dynamics Yangyang Wang, Zhiqiang Shen, Jan-Michael Y Carrillo, Bobby G Sumpter A recently proposed two-dimensional analysis approach is applied to investigate mesoscopic liquid dynamics. Using molecular dynamics simulations, the pressure and collective density correlations of several model glass-forming liquids are spatiotemporally mapped on a dense grid of correlation times and wavenumbers. It is shown that many features of these correlation functions in the mesoscopic regime can be qualitatively described by the classical hydrodynamic theories. Signatures of nonhydrodynamic behavior are also identified. |
Friday, March 18, 2022 8:24AM - 8:36AM |
Y02.00003: Liquid-liquid Phase Transition in Supercooled H2O and D2O: A Path-Integral Computer Simulation Study Ali H Eltareb We perform path-integral molecular dynamics (PIMD) and classical MD simulations of H2O and D2O using the q-TIP4P/F water model over a wide range of temperatures and pressures. The density ρ(T), isothermal compressibility κT(T), and self-diffusion coefficients D(T) of H2O and D2O are in excellent agreement with available experimental data; the isobaric heat capacity CP(T) obtained from PIMD and MD simulations agree qualitatively well with the experiments. Some of these thermodynamic properties exhibit anomalous maxima upon isobaric cooling, consistent with the recent experiments and with the possibility that H2O and D2O exhibit a liquid-liquid critical point (LLCP) at low temperatures and positive pressures. The data from PIMD/MD for H2O and D2O can be fitted remarkably well using the Two-State-Equation-of-State (TSEOS). Using the TSEOS we find that the differences in the LLCP location from PIMD and MD simulations of H2O and D2O suggest that nuclear quantum effects play an important role in the thermodynamics of water around the LLCP. Overall, our results strongly support the LLPT scenario to explain water anomalous behavior, independently of the fundamental differences between classical MD and PIMD techniques. |
Friday, March 18, 2022 8:36AM - 8:48AM |
Y02.00004: Understanding the fragile-to-strong transition in silica from microscopic dynamics Zheng Yu, Ajay Annamareddy, Dane Morgan, Bu Wang In this work, we revisit the fragile-to-strong (FTS) transition in the simulated BKS silica from the perspective of microscopic dynamics, in an effort to elucidate the dynamical behaviors of fragile and strong glass forming liquids. Softness, which is a machine-learned feature from local atomic structures, is used to predict the microscopic activation energetics and long-term dynamics. The FTS transition is found to originate from a change in the temperature dependence of the microscopic activation energetics. Furthermore, results suggest there are two diffusion channels with different energy barriers in BKS silica. The fast dynamics at high temperatures is dominated by the channel with small energy barriers (< ~1 eV), which is controlled by the short-range order. The rapid closing of this diffusion channel when lowering temperature leads to the fragile behavior. On the other hand, the slow dynamics at low temperatures is dominated by the channel with large energy barriers controlled by the medium-range order. This slow diffusion channel changes only subtly with temperature, leading to the strong behavior. The distributions of barriers in the two channels show different temperature dependences, causing a crossover at 3,100 K. This transition temperature in microscopic dynamics is consistent with the inflection point in the configurational entropy, suggesting there is a fundamental correlation between microscopic dynamics and thermodynamics. |
Friday, March 18, 2022 8:48AM - 9:00AM |
Y02.00005: Chirality transfer induced in a lead-halide perovskite cluster through sruface chemistry modification Amanda J Neukirch, Aaron A Forde, Dibyajyoti Ghosh, Amanda C Evans, Sergei Tretiak The chiroptical properties of materials are of interest for various applications, including structure determination, polarized photo-detectors/luminescence sources, and spintronics. Inducing chiroptical activity into semiconductors is a challenge due to the difficulty of controllably creating asymmetric crystal structures. One promising method is chirality transfer by capping nanocrystals with chiral organic ligands. Experimentally, chiral capped nanocrystals show emergent chiroptical signatures, but the mechanisms for chirality transfer remain unclear. We utilize TDDFT to explore chirality transfer in CsPbX3 (X=Cl, I) clusters capped with chiral diaminocyclohexane (DACH) enantiomers. When DACH is bound to the cluster surface, perovskite optical transitions gain chiroptical activity that is dependent on the binding configuration. We find that this chirality transfer is best rationalized by the coupling of the static dipoles from the adsorbed chiral molecules to the optical transition dipole of the perovskite cluster. The ratio of circular dichroism to absorption, known as the anisotropy factor, increases proportionally to surface ligand density and provides mechanistic insight for improving the chiroptical functionality of semiconductor nanomaterials. |
Friday, March 18, 2022 9:00AM - 9:12AM |
Y02.00006: The effect of CdSe nanoparticles on the optical properties of Pr3+ ions in bismuth boro-tellurite glasses P. K Babu, Saisudha B Mallur Glasses are ideal host for rare-earth (RE) ions. The optical properties of RE ions can be varied by modifying their chemical environments through compositional changes or by having metal/semiconducting nanoparticles grown inside these gasses. We studied the influence of CdSe nanoparticles on the optical properties of Pr3+ doped bismuth boro-tellurite glasses. In order to grow these nanoparticles, CdSe powder is added with the starting materials while preparing the glasses using the melt-quench technique. These glasses are then subjected to a process of controlled annealing near the glass transition temperature. During this annealing process, CdSe molecules that are uniformly dispersed in the glass matrix undergo thermal diffusion and coagulate to form nanoparticles. The average size of these nanoparticles can be changed by varying the duration of the annealing. Our studies show that the Pr-O bond becomes less covalent when CdSe nanoparticles are present in the glass. Glasses with CdSe nanoparticles show significant enhancement for the stimulated emission cross section of Pr3+ fluorescence. The presence of larger CdSe nanoparticles can considerably enhance the nature and the intensity distribution of the light emitted by these glasses. |
Friday, March 18, 2022 9:12AM - 9:24AM |
Y02.00007: Nanoscale Characterization of Energetic Core-Shell Carbon-coated Aluminum Nanoparticles Produced via Atmospheric Plasma Surface Treatment Dinesh Thapa, Lily Giri, Rose A Pesce-Rodriguez, Scott D Walck, Benjamin Evangelisti, Chi-Chin Wu Aluminum nanoparticles (nAl) have received considerable attention as metallic fuels due to their high heat of combustion, enhanced oxidation reactivity and large specific surface area to volume ratio. However, nAl are usually covered with a passivated amorphous oxide shell, which is detrimental for their intended applications. In this work, the key characterization results will be presented for our new reactive carbon coated nAl (nAl@C) samples produced by a two-step atmospheric plasma surface treatment process. This involved initial helium (He) plasma treatment of commercial nAl particles, followed by He/carbon monoxide (CO) plasma treatment for different durations. The resulting nAl@C were comprehensively studied utilizing advanced microscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy. High-resolution transmission electron microscopy (HRTEM) images revealed a distinct faceted core/shell structure with significantly reduced oxide shell of nAl after the He plasma treatment at the first step. An evenly distributed carbonaceous material on the surface of Al@C was confirmed. The carbonaceous materials was determined to be aluminum carboxylate via Fourier transform infrared spectroscopy. The results from the reactive molecular simulation will be discussed in relevance to some our experimentally observed results. |
Friday, March 18, 2022 9:24AM - 9:36AM |
Y02.00008: How Quantum are Titan's Minerals? Exploring Structure, Dynamics, and Nuclear Quantum Effects in Organic Co-Crystals. Atul C Thakur, Richard C Remsing Titan – Saturn’s largest moon and perhaps the most ‘Earth-Like’ planetary body within our solar system is reported to possess an arsenal of organic molecules which can condense onto Titan’s surface in the form of stable surface liquids and organic co-crystals, examples of which include the acetylene-ammonia and benzene-ethane co-crystals. Such an array of organic minerals are important to Titan’s surface geology and could even promote a prebiotic chemical evolution by facilitating a variety of bulk and surface phenomena though their rich phase behavior. We investigate the presence of dynamically disordered phases within acetylene-ammonia co-crystals using density functional theory-based ab-initio molecular dynamics simulations. By quantifying molecular rotational dynamics within acetylene-ammonia co-crystals, we show evidence of the rotator phase of ammonia molecules possessing a discrete rotational symmetry. Given the cryogenic surface conditions of Titan (~90 K ), quantum effects of the nuclei could further impact the dynamics within these co-crystals. Therefore, we also investigate the role of nuclear quantum effects on the rotator phase using ab-initio path integral molecular dynamics simulations. We find that nuclear quantum effects significantly accelerate the rotational diffusion of ammonia molecules within the acetylene-ammonia co-crystal. We rationalize the observed orientational diffusion in terms of transient breakage and reformation dynamics of N-H…π hydrogen bonds within the crystal. We discuss our findings within the broader context of understanding fundamental physical processes occurring within organic co-crystals beyond Titan’s surface, which could have significant implications for pharmaceuticals, solid-state electrolytes, and organic semiconductors. |
Friday, March 18, 2022 9:36AM - 9:48AM |
Y02.00009: Real-space Dynamics in Aqueous Salt Solution Yuya Shinohara, Ray Matsumoto, Matthew W Thompson, Wojciech Dmowski, Chae Woo Ryu, Daisuke Ishikawa, Alfred Q Baron, Peter T Cummings, Takeshi Egami, Takuya Iwashita We report on the real-space correlated motion of water molecules and ions in an aqueous salt solution. The Van Hove functions–pair-correlation functions in space and time–of aqueous salt solution were determined by high-resolution inelastic X-ray scattering (IXS) spectra over a wide range of momentum transfer and energy transfer as well as molecular dynamics simulation. (Pseudo-) Partial Van Hove function was determined to disentangle the element-specific correlated motions. Our results directly depict the distance-dependent correlated dynamics of aqueous salt solutions in picosecond timescale and identify the changes in the anion–water and cation–water correlations. We found that the ion–water correlations show a two-step relaxation, which corresponds to a local rattling-like vibration and the local configurational rearrangement. |
Friday, March 18, 2022 9:48AM - 10:00AM |
Y02.00010: Structure property relations in (As2Se3)x(GeTe4)100-x glasses Shweta Chahal Bulk (As2Se3)x(GeTe4)100-x glasses have been prepared over the entire composition range 0 ≤ x ≤ 100. In this tie-line, the average coordination number (Zav) of all the glasses is 2.40 at which the constraints acting on the network and the number of degrees of freedom are balanced. Glass transition (Tg) and non-reversing heat flow (ΔHnr) determined from DSC and MDSC measurements exhibit interesting variations with composition. Based on these variations the structural network can be divided into three regions: (I) 0 ≤ x ≤ 20 (II) 25 ≤ x ≤ 45 and (III) 50 ≤ x ≤ 100. Both Tg and ΔHnr show a decreasing trend in the region I and remain invariant in the region II. In the region III, Tg and ΔHnr show an increasing trend. From the Raman measurements we infer that the network in the region I is dominated by the GeTe4/2 tetrahedral units. The addition of As2Se3 initially depolymerizes the network due to which a decrease in Tg is observed in the region I. The region II is dominated by the AsTe3/2 pyramidal units and Te-Te chains. In this region, the network starts polymerizing and at the same time there is a decrease in the mean bond energy. These two factors compete with each other and hence both Tg and ΔHnr remains invariant. The region III is rich with As2Se3 and the structural network is dominated by AsSe3/2 structural units. Both network connectivity and the mean bond energy go hand in hand in this region and there is an increase in the Tg and ΔHnr. For 25 ≤ x ≤ 45, ΔHnr almost vanishes indicating non aging of the glasses in the region II. This study underlines the effects of chemical composition and the mean bond energy variations in a critically coordinated covalent network. |
Friday, March 18, 2022 10:00AM - 10:12AM |
Y02.00011: Dielectric Profile and Electromelting of a Monolayer of Water Confined in Graphene Slit Pore JEET MAJUMDAR, Mohd Moid, Chandan Dasgupta, Prabal K Maiti Monolayer confined water between parallel graphene sheets exists in many different phases and exhibits fascinating dielectric properties that have been studied in experiments. We use molecular dynamics simulations to study how the dielectric properties of a confined monolayer of water is affected by its structure. Considering six nonpolarizable water models we investigate the role of the in-plane water structure on its dielectric profile. We find that models which do not exhibit ice formation show very different dielectric response along the channel width compared to models that exhibit square ice formation. We also demonstrate the occurrence of electromelting of the in-plane ordered water under the application of a perpendicular electric field and find the model-dependent critical field values. Together, we have shown the strong dependence of confined water properties on the different water structures that can be exploited in various nanofluidic devices, artificial ion channels, and molecular sieving. |
Friday, March 18, 2022 10:12AM - 10:24AM |
Y02.00012: Solvation free energies of molecules and ions: a first principles study Junting Yu, Ding Pan The solvation free energy of molecules or ions is a fundamental quantity to study the properties of aqueous solutions. There are various computational methods to calculate this quantity, but many of them reply on experimental inputs or empirical models. Here, we introduce a first-principles method to calculate this quantity accurately and efficiently. Our method is based on ab initio molecular dynamics and thermodynamic integration. As an example, we calculated the solvation free energies of methane, methanol, water molecules and the Na+ ion in water at ambient conditions and compared them with experimental data. Because our method does not need any experimental input, it can be readily used to study supercritical aqueous solutions at elevated pressure and temperature conditions, where experimental data are scarce. Our method can be also easily implemented with machine learning force fields. |
Friday, March 18, 2022 10:24AM - 10:36AM |
Y02.00013: Crystal nucleation and liquid-liquid transition in deeply supercooled silicon Srikanth Sastry, Yagyik Goswami, Vishwas Vasisht, Pablo G Debenedetti, Daan Frenkel The possibility of a liquid-liquid phase transition in several network-forming liquids such as water, silica and silicon has been intensely investigated over several years. In the majority of cases these putative transitions occur at conditions far below the melting temperature. Under such conditions, the kinetics of crystallisation in principle poses a challenge towards observing such a transition. In fact, it has been argued, on the basis of reversible free energy calculations, that the evidence points instead towards slow, but spontaneous, crystallisation. Robust evidence of well-defined metastable liquid states and a liquid-liquid transition has been found for a number of models of water. These studies also show a clear free energy barrier to crystallisation under the relevant conditions. We study crystal nucleation in liquid silicon through computer simulations of a classical model, with the aim of answering the specific question of whether a well-defined metastable liquid exists under the relevant conditions. We find, that indeed a barrier to crystallisation exists, and that the choice of order parameter is crucial. We also discuss the effect of changes in the microscopic structure of the liquid on the free energy barriers to crystallisation. |
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