Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session A25: Chemical Physics of Liquids, Glasses, and CrystalsLive
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Sponsoring Units: DCP Chair: N. Aluru, University of Illinois at Urbana-Champaign |
Monday, March 15, 2021 8:00AM - 8:12AM Live |
A25.00001: Stimulated Emission Cross Sections and Quantum Efficiencies of Sm3+ and Sm3+-Eu3+ Co-doped Bismuth Boro-tellurite Glasses P K Babu, Saisudha B Mallur, Ting C Khoo, Suman Rijal, Owen R Huff The effect of host glass composition and co-doping with Eu3+ on the optical properties of Sm3+ has been investigated in bismuth boro-tellurite glasses. The intensity parameters Ωt (t=2,4,6), radiative transition probability (Arad) and radiative lifetimes (τrad) are obtained from optical absorption studies. Excitation spectra show that there exists energy transfer from Sm3+ to Eu3+ and vice versa. From fluorescence studies, fluorescence decay time (τexp), radiative quantum efficiencies (η), branching ratios (β) and peak stimulated emission cross section (σp) are obtained. The highest η of Sm3+ doped bismuth boro-tellurite glasses is found to be 60% and for Sm3+-Eu3+ co-doped glasses, it is 74%. Changing the host glass composition and co-doping with Eu3+ ions, the η of the glasses can be improved. The σp of Sm3+-Eu3+ doped glasses is found to be larger than that of singly doped Sm3+ glasses. Our results indicate that modifying the host glass composition and co-doping with Eu3+ can improve the emission characteristics of Sm3+ ions. Bismuth boro-tellurite glasses with enhanced values for η and σp are suitable for photonic devices and photovoltaic applications. |
Monday, March 15, 2021 8:12AM - 8:24AM Live |
A25.00002: Nuclear Quantum Effects in ab initio Water Models Amartya Bose, Roberto Car Quantum nuclear effects can play a subtle but significant role in properties of water. However accurate fully quantum simulations of dynamics in condensed phase media is computationally intractable. Among the various classical trajectory based approaches, Wigner dynamics is lucrative because it can be derived as a linearization of the path integral expressions. The primary challenge is to estimate the Wigner density which involves a multidimensional Fourier transform. Various approximations to the Wigner density are possible. Irrespective of the approximation used, the cost of these simulation for ab initio density functional theory (DFT) used to make it untenable. Recent developments in the framework of Deep Molecular Dynamics (DeepMD) allows the usage of machine learning models fit to high quality DFT potential energy surfaces. These models have been used to study the classical dynamics of water at unprecedented levels of accuracy. We evaluate and compare the impact of quantum nuclear effects on the dynamical properties of these water models using different approximations to Wigner dynamics. |
Monday, March 15, 2021 8:24AM - 8:36AM Live |
A25.00003: Cluster mediated self-hydrolysis of γ-Al(OH)3 to γ-AlOOH Jack Simonson, Alicia M. Baccarella, Rhiannon Garrard, Michelle Beauvais, Urszula Bednarksi, Steven Fischer, Olaf J. Borkiewicz, Milinda Abeykoon, Karena Chapman, Brian Phillips, John B. Parise We report a mechanism by which γ-Al(OH)3 is converted to γ-AlOOH through hydrothermal reaction at 473 K. X-ray pair distribution function measurements indicate that γ-Al(OH)3 decomposes to amorphous clusters upon contact with water, while nanocrystalline γ-AlOOH precipitates within 1 h of hydrothermal exposure. Solid state nuclear magnetic resonance measurements show that resonant features associated with four- and five-member Al clusters persist through 20~min of hydrothermal treatment, while ultraviolet (UV) spectra mark the onset of UV-induced photoluminescent features characteristic to γ-AlOOH with 10 min of exposure, indicating a coexistence region of γ-Al(OH)3-like and γ-AlOOH-like amorphous species. Powder x-ray diffraction measurements of desiccated powders reveal that the conversion process takes place in three distinct, power law-defined stages with initial γ-AlOOH nucleation occurring within the first 20 min, followed by a ~1 h period of rapid grain coarsening and the subsequent onset of Lifshitz-Slyozov-Wagner-like coalescence. |
Monday, March 15, 2021 8:36AM - 8:48AM Live |
A25.00004: The glass transition temperature of co-amorphous molecular glasses with strong interactions xiao zhao, Sixue Cheng, Yung P. Koh, Gregory B McKenna, Sindee L Simon The glass transition temperature (Tg) of binary miscible mixtures of molecular glasses, termed co-amorphous materials, is often synergistically increased over the Tg of the two components. This synergy is thought to arise from the strong interactions between the two species, and it is particularly important for pharmaceutical co-amorphous formulations, where Tg and the molecular interactions between the components of the co-amorph are important for determining the shelf life of the drug, its stability against crystallization and phase separation, its dissolution kinetics, and its in-vivo precipitation. Current models that describe the compositional dependence of Tg, including the Gordon-Taylor, Braun-Kovacs, and Kwei equations, fail to predict the Tg increases observed in co-amorphous pharmaceutical systems with strong interactions. In this study, a robust thermodynamic framework is developed extending Gordon and Taylor’s configurational entropy approach using the excess entropy and models of the activity coefficient, in order to model Tg of several pharmaceutical co-amorphous molecular mixtures. The non-random two-liquid (NRTL) activity coefficient model well describes the synergistic increase in Tg in these systems. |
Monday, March 15, 2021 8:48AM - 9:00AM Live |
A25.00005: Nuclear Quantum Effects on the Thermodynamic, Structural, and Dynamical Properties of Equilibrium and Supercooled Water Ali Eltareb, Nicolas Giovambattista, Gustavo E Lopez We perform path-integral molecular dynamics (PIMD) simulations of H2O and D2O using the qTIP4P/F model. Simulations are performed at P = 1 bar and for temperatures 200 < T < 375 K. The density of H2O and D2O calculated from PIMD simulations are in excellent agreement with experiments at T > 230 K. We also evaluated the thermal expansion coefficient αp(T), isothermal compressibility κT(T), isobaric heat capacity CP(T), and the dielectric permittivity ε(T). We found that at T > 273 K, αP(T) and κT(T) are in perfect agreement with experiments while CP(T) and ε(T) are in semi-quantitative agreement. However, deviations between PIMD simulations and experiments, become more pronounced upon supercooling implying that the inclusion of nuclear quantum effects in PIMD simulations of qTIP4P/F water are not sufficient to reproduce the large fluctuations in density and entropy characteristic of supercooled water. We also calculated the diffusion coefficient of H2O and D2O using the ring-polymer molecular dynamics (RPMD) approach and find that computer simulations are in good agreement with experiments at all temperatures studied. Our results from PIMD simulations are not inconsistent with the possibility that H2O and D2O exhibit a liquid-liquid critical point at low temperature. |
Monday, March 15, 2021 9:00AM - 9:12AM Live |
A25.00006: Contribution of atom vibrations to the latent heat of germanium Camille Bernal, Claire Saunders, Stefan Haegeli Lohaus, Rebecca Mills, Douglas L Abernathy, Brent Fultz There is general agreement that atomic vibrations dominate the entropy of solid and liquid phases of materials. The changes of vibrational and configurational entropies upon melting are expected to be responsible for the latent heat, L = TΔS, but the relative importance of each is largely unknown today. Here, we report the vibrational spectra of germanium from 300-1373K measured with ARCS, a high flux direct geometry neutron spectrometer. Inelastic neutron spectra at temperatures below, near, and above the melting temperature of germanium (Tm = 1211K) allowed for direct assessment of the role of vibrational thermodynamics during melting. A large collapse of the higher frequency modes in the solid to lower frequencies was observed upon melting. Analysis of the vibrational spectra across the melting transition showed that at most 60% of the entropy of melting originates from the lower frequencies of atomic motion in the liquid phase. The remainder is probably from the larger configurational entropy of the liquid. Classical and ab-initio calculations are being performed to assess the change in phonon frequencies with temperature, and across the melting transition. |
Monday, March 15, 2021 9:12AM - 9:24AM Live |
A25.00007: Four-Dimensional Scaling of Dipole Polarizability in Quantum Systems Peter Szabo, Szabolcs Goger, Jorge Charry, M. Reza Karimpour, Dmitry Fedorov, Alexandre Tkatchenko Polarizability is a key response property of classical and quantum systems, which has an impact on intermolecular interactions, spectroscopic observables, and vacuum polarization. The calculation of polarizability for quantum systems involves an infinite sum over all excited (bound and continuum) states, concealing the physical interpretation of polarization mechanisms and complicating the derivation of efficient response models. Approximate expressions for the dipole polarizability, α, rely on different scaling laws α ∝ R3, R4, or R7, for various definitions of the system radius R. In this work, we consider a range of quantum systems of varying spatial dimensionality and having qualitatively different spectra, demonstrating that their polarizability follows a universal four-dimensional scaling law α=C(4μq2/h2)L4, where μ and q are the (effective) particle mass and charge, C is a dimensionless constant of order one, and the characteristic length L is defined via the L2-norm of the position operator. The applicability of this unified formula is demonstrated by accurately predicting molecular polarizabilities from the effective polarizability of their atomic constituents. |
Monday, March 15, 2021 9:24AM - 9:36AM Live |
A25.00008: Many-body plane wave-basis set simulations and their applicability within quantum algorithms for electronic structure Stephen Cotton, Norm Tubman Although atom-centered Gaussian basis sets are used ubiquitously in conventional quantum chemistry codes to solve the electronic Schrodinger Eq., on quantum processors, the favorable-scaling of the quantum version of the fast Fourier transform (FFT) makes orbital representations in terms of underlying plane-wave basis functions a potentially superior option, possibly even for non-periodic systems. Developed in this work are estimates of the number of plane-waves needed in a full (or selective) configuration interaction (CI) calculation to achieve a desired accuracy for various standard isolated atomic and molecular systems. This is achieved by re-expressing the usual 1- and 2-body electronic integrals in terms of orbitals decomposed into Fourier components subjected to a kinetic energy cutoff. It is found that the number of plane-waves required depends heavily on the extent to which the original Gaussian basis-optimized orbitals are localized in real-space and hence, essentially, on the atomic numbers of the constituent atoms. For larger atomic numbers, even if one invokes the frozen-core approximation, it is estimated that many millions of plane-waves are required to adequately represent the most highly-localized molecular orbitals and to calculate CI energies to high accuracy. |
Monday, March 15, 2021 9:36AM - 9:48AM On Demand |
A25.00009: Deep Learning Enabled Holographic Polarization Microscopy Tairan Liu, Kevin de Haan, Bijie Bai, Yair Rivenson, Yi Luo, Hongda Wang, David Karalli, Hongxiang Fu, Yibo Zhang, John FitzGerald, Aydogan Ozcan Polarization microscopy has long been used in various fields due to its unique capability of highlighting birefringent objects. Traditional polarization microscopy techniques usually require the collection of two or more images from light paths with different polarization states to either enhance the image contrast or retrieve quantitative information of birefringent specimen. Because of this, these methods typically have complex optical designs and require experienced technicians to operate. Here, we present a deep learning-based holographic polarization microscopy framework which transforms the holographic amplitude and phase information of a sample into the birefringent retardance and orientation channels. This framework only requires the addition of one polarizer/analyzer pair to an existing lensfree holographic imaging system, with a compact optical design and a large field of view (~20-30 mm2). We experimentally tested this framework with different types of birefringent samples including monosodium urate (MSU) crystals, showing its capability to accurately reconstruct quantitative birefringence information of specimen. |
Monday, March 15, 2021 9:48AM - 10:00AM On Demand |
A25.00010: Exceptional elastic properties in amorphous solids by modulating oscillatory interatomic potentials Jaeyun Moon, Takeshi Egami Numerous methods have been proposed to enhance elastic properties in amorphous solids, typically by inclusion of highly elastic materials or elements. However, a precise physical understanding of these enhancements is lacking due to numerous variables in play such as chemical concentrations, crystallinity, density, and others, leading to difficulties to optimize elastic properties. In this work, we present a novel bottom-up strategy to achieve exceptionally high bulk and shear modulus in amorphous solids by introducing long range oscillatory atomic interactions mimicking the Friedel oscillations. We demonstrate the strategy in molecular dynamics simulations on monatomic glasses of same density with various interaction cutoff distances. We find that by enlarging the cutoff distance of the oscillatory potentials by a few Å, both bulk and shear modulus sharply increase by nearly a factor of 2, suggesting that modulating long range oscillatory atomic interactions is an effective route in realizing extraordinary elastic properties in amorphous solids. |
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