Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session Y16: Complex Soft Materials 
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Sponsoring Units: GSOFT Chair: Troy Shinbrot, Rutgers University Room: 275 
Friday, March 17, 2017 11:15AM  11:27AM 
Y16.00001: Toward reducedorder modeling techniques in granular media Ken Kamrin, Hesam Askari, Dan Goldman, Qiong Zhang, Stephen Townsend 
Friday, March 17, 2017 11:27AM  11:39AM 
Y16.00002: Abstract Withdrawn We investigate the electrostatic charging of an agitated bed of identical grains using simulations, mathematical modeling, and experiments. We simulate charging with a discreteelement model including electrical multipoles and find that infinitesimally small initial charges can grow exponentially rapidly. We propose a mathematical Turing model that defines conditions for exponential charging to occur and provides insights into the mechanisms involved. Finally, we confirm the predicted exponential growth in experiments using vibrated grains under microgravity, and we describe novel predicted spatiotemporal states that merit further study. 
Friday, March 17, 2017 11:39AM  11:51AM 
Y16.00003: Combined effect of moisture and electrostatic charges on powder flow Geoffroy Lumay, Antonella Rescaglio, Julien Schockmel, Nicolas Vandewalle It is well known in industrial applications involving powders and granular materials that the relative air humidity and the presence of electrostatic charges influence drastically the material flowing properties. The relative air humidity induces the formation of capillary bridges and modify the grain surface conductivity. The presence of capillary bridges produces cohesive forces. On the other hand, the apparition of electrostatic charges due to the triboelectric effect at the contacts between the grains and at the contacts between the grains and the container produces electrostatic forces. Therefore, in many cases, the powder cohesiveness is the result of the interplay between capillary and electrostatic forces. Unfortunately, the triboelectric effect is still poorly understood, in particular inside a granular material. Moreover, reproducible electrostatic measurements are difficult to perform. We developed an experimental device to measures the ability of a powder to charge electrostatically during a flow in contact with a selected material. Both electrostatic and flow measurements have been performed in different hygrometric conditions. The correlation between the powder electrostatic properties, the hygrometry and the flowing behavior are analyzed. [Preview Abstract] 
Friday, March 17, 2017 11:51AM  12:03PM 
Y16.00004: Breaking Propensity: A destructive method seeking structures which determine particle motion. Cordell Donofrio, Eric Weeks It is known that at any given time in a supercooled liquid, particles can be found that have a higher propensity to move. This is found by running simulations with repeated initial positions but with shuffled initial velocities, and observing that some particles are in positions for which they frequently have large displacements. This suggests that local structure may play an important role, and that it may be possible to distinguish ahead of time which particles have a higher propensity for motion. We investigate the magnitude of this effect by simulating the KobAndersen binary LennardJones glass former, and measure the propensity signal over a large range of time scales. Additionally, we attempt to 'break' this signal by introducing structural changes, thereby revealing key structural features related to propensity. [Preview Abstract] 
Friday, March 17, 2017 12:03PM  12:15PM 
Y16.00005: Anomalous Diffusion and Stress Relaxation in Micellar Fluids Radhakrishna Sureshkumar, Subas Dhakal This talk will address two longstanding questions on the dynamics and rheology of micellar fluids. First, it has long been hypothesized that branched micelles are much more efficient in relaxing internal stresses than linear ones via sliding of branches along main chain contours. Second, anomalous surfactant diffusion including superdiffusion has been suggested by experiments. Tracking the motion of branch points as well as individual surfactants poses a great challenge. We use molecular dynamics simulations of cationic surfactant solutions of cetyltrimethylammoniumchloride in the presence of a hydrotropic salt sodium salicylate to answer the above questions. The mechanisms of branch formation, superdiffusion and the energetics of branch motion will be discussed. ~ [Preview Abstract] 
Friday, March 17, 2017 12:15PM  12:27PM 
Y16.00006: Thermal processing routes to structure control in phase separating colloidal gels Tuan Nguyen, Yongxiang Gao, Juntae Kim, Matthew Helgeson Sophisticated thermal quenching and annealing strategies to create bicontinuous or hierarchical morphology have allowed for the creation of molecular materials (metals, ceramics, minerals and polymers) with significantly enhanced properties. Here, we explore new routes by which similar thermal processing strategies can be applied to colloidal gels. Specifically, colloidpolymer mixtures with thermoresponsive bridging attractions are employed to characterize how the thermal path taken through regions of nonequilibrium phase separation and gelation determine the dynamics and arrest of colloidal gelation. Interestingly, we find that the dominant mechanism of gelation (percolation, arrested phase separation or attractive glass formation) is highly sensitive to both the colloid volume fraction as well as the nonequilibrium thermodynamic path to the gelled state. Using recentlydeveloped Fourier correlation microscopy methods, we show that this sensitivity is due to the temperature dependence of competing time scales for diffusion, aggregation and phase separation. Ultimately, we show how the control of these dynamics by thermal processing can be used to tailor the microstructure and rheology of colloidal gels. [Preview Abstract] 
(Author Not Attending)

Y16.00007: Melt Structure Evolution of CuZrTi Metallic Glasses Rohan Mishra, Anupriya Agrawal, Katharine M. Flores, Kenneth F. Kelton Studying the evolution of melt structure of metallic glasses as we approach their glass transition temperature is essential to understand glass formation. Known for their excellent glass forming ability, CuZr binary metallic glasses are very well studied in the literature. Here, we have focused on CuZrTi ternary metallic glasses in order to extend the current understanding of metallic glasses to more complex and eventually more realistic glasses. We have used molecular dynamics simulations to characterize the changes in the structure and dynamics of (Cu$_{\mathrm{50}}$Zr$_{\mathrm{50}})_{\mathrm{1}}_{x}$Ti$_{x}$ (\textit{0 \textless x \textless } 1) melt with the quenching. We observe that compositions with$ x$ \textless 0.5 form glassy solid and with$ x$ \textgreater 0.6 form crystalline solid for the same quench rates which agrees well with the experimental findings. Here, we have explored the factors that govern if a melt will form a glassy or crystalline solid. We will show that the overall density and dynamics doesn't have significant effect on solidification path the melt will follow. We will focus on the short and medium range order of the melt and their diffusion as a function of composition and temperature to highlight the differences in the melt behavior of the amorphous glasses from their crystalline form. [Preview Abstract] 
Friday, March 17, 2017 12:39PM  12:51PM 
Y16.00008: IoffeRegel localization of longitudinal acoustic excitations and the Arrhenius crossover regime in glassforming metallic liquids Abhishek Jaiswal, Yang Zhang The IoffeRegel (IR) criterion is known to distinguish the boundary between propagating and localized excitations. In previous studies of liquids the localization of transverse excitations within atomic cages at hightemperature has been elucidated using the IR limit. Much less emphasis has been put on the nature of longitudinal excitations and the IR limit. Herein, we map out the wavelength dependent IR crossover temperature of the longitudinal excitations in an excellent CuZrAl based glassformer. We find that the inflection point of this map occurs at the Arrhenius crossover temperature $T_{A}$ identified from deviations of Arrhenius form in transport properties and the breakdown of StokesEinstein relation. The corresponding wavelength of longitudinal excitations at $T_{A}$ equals the limit where all partial pair distribution functions $g(r)$ of the liquid approaches the random structure limit, essentially marking the boundary between the discrete and the continuous liquid. This map allows us to extract a temperature range for the Arrhenius crossover or the landscapeinfluenced regime in a glassforming liquid. [Preview Abstract] 
Friday, March 17, 2017 12:51PM  1:03PM 
Y16.00009: Topological phases in (Na$_{2}$O)$_{x}$(P$_{2}$O$_{5})_{100x}$ glasses. Chandi Mohanty, Ralph Chbeir, Andrew Czaja, Ping Chen, Punit Boolchand We have synthesized titled glasses in the 0 \textless x \textless 0.50 range of soda paying special attention to their dryness. Pure P$_{2}$O$_{5}$ glass was synthesized by flash evaporation of bulk powder in a quartz tube as it was pumped in several attempts, and the variation of T$_{g}$ and enthalpy of relaxation ($\Delta $H$_{nr})$ measured for each attempt. These data show that as the glass got drier, T$_{g}$ increased to 431\textdegree C and $\Delta $H$_{nr}$ became miniscule. At higher soda content (x \textgreater 20{\%}), T$_{g}$(x) increased steadily, but with appearance of a local maximum near x $=$ 37.5{\%}. On the other hand $\Delta $H$_{nr}$ term, revealed a Trapezoidallike minimum in the 32.5 {\%} \textless x \textless 42.5{\%} range, suggestive of a reversibility window or the isostatically rigid Intermediate Phase, with glasses at x \textgreater 42.5{\%} in the flexible phase while those in the 20{\%} \textless x \textless 32.5{\%} range in the stressed rigid phase. We have also obtained Raman scattering, IR reflectance and fragility index measurements on the present glasses, and these will discussed with recent$^{1}$ results in the field. \begin{enumerate} \item D.L. Sidebottom J. Chem. Phys. \textbf{140}, 154501(2014). \end{enumerate} [Preview Abstract] 
Friday, March 17, 2017 1:03PM  1:15PM 
Y16.00010: Slow homogenization of binary AsS melts and vibrational evidence of As QuasiTetrahedral Units in glasses. Soumendu Chakravarty, Shreeram Dash, Ralph Chbeir, Ping Chen, Punit Boolchand FTRaman profiling experiments on binary AsS melts are undertaken to establish the kinetics of homogenization of 1gram batch sizes using As$_{\mathrm{2}}$S$_{\mathrm{3}}$ and dry S as starting materials. These data reveal that melts take typically 3 weeks of reaction at 700\textdegree C to homogenize. Such slow kinetics of melt homogenization were noted earlier in Ge  S binary and reflect the superstrong$^{\mathrm{1}}$ character (fragility index m \textless 20) of melts in the Intermediate Phase$^{\mathrm{1}}$ composition range. An important consequence of these homogenization experiments is that the Raman active 537 cm$^{\mathrm{1}}$ mode predicted$^{\mathrm{2}}$ for the stretch vibration of S$=$As of Quasi Tetrahedral S$=$As(S$_{\mathrm{1/2}})_{\mathrm{3}}$ units is now observed in homogeneous glasses. Compositional trends of the mode scattering strengths, fragility index and the non  reversing enthalpy of relaxation at T$_{\mathrm{g}}$ in these homogeneous glasses will be presented. \item S. Chakravarty, and P. Boolchand, J. Phys. Chem. B 118, 2249(2014). \item P. Chen et al. Phys. Rev. B 78, 224208 (2008). [Preview Abstract] 
Friday, March 17, 2017 1:15PM  1:27PM 
Y16.00011: Intermediate Phase Spectroscopy of (Na$_{\mathrm{2}}$O)$_{\mathrm{x}}$[(B$_{\mathrm{2}}$O$_{\mathrm{3}})_{\mathrm{y}}$(GeO$_{\mathrm{2}})_{\mathrm{1y}}$]$_{\mathrm{1x}}$ glasses Aaron Welton, Ralph Chbeir, Andrew Czaja, Punit Boolchand The titled ternary is of interest because the two end members, viz., y$=$ 0, i.e., Sodium Germanate $^{\mathrm{1}}$, and y $=$ 1, Sodium Borate $^{\mathrm{2}}$ have been studied earlier and show the isostatically rigid Intermediate Phase (IP) to occur in the x $=$ 0.14 to x $=$ 0.19 range and in the x $=$ 0.20 to x $=$ 0.40 range of soda respectively. In the present work we now report on bulk glasses at y $=$ 0.75 synthesized over a wide range x $=$ 0 to x $=$ 0.30 of soda. Our motivation is to understanding the evolution of the IP in the pseudoternary glasses as the base glass connectivity is altered. Preliminary MDSC experiments show T$_{\mathrm{g}}$(x) to increase with x and to reveal a broad maximum at 510 C centered near x $=$ 0.25. Furthermore, an IP is found in the x $=$ 0.20 to x $=$ 0.33 range of soda where a reversibility window is observed. The window is centered near the T$_{\mathrm{g}}^{\mathrm{max}}$ content at x$=$ 0.25. IR reflectance show modes of BO$_{\mathrm{4}}$ and BO$_{\mathrm{3}}$ units but also those of bonded water. Raman scattering largely shows modes observed earlier in Sodium borate glasses$^{\mathrm{2}}$. 1 V. Rompicharla et al. J PCM 20, 202101 (2008) 2K. Vignarooban et al. EPL 108, 56001(2014). [Preview Abstract] 
Friday, March 17, 2017 1:27PM  1:39PM 
Y16.00012: Topological Phases in AlkalineEarth Borates Ralph Chbeir, Chad Holbrook, Andrew Czaja, Punit Boolchand Raman scattering has proved to be a powerful method to probe local, intermediate ( rings) and extendedrange (structural groupings) structure in Li and NaBorates$^{\mathrm{1}}$ and BaBorates$^{\mathrm{2}}$. Along with AC calorimetric (MDSC) data on non reversing enthalpy of relaxation, we could identify the Stressedrigid, Intermediate and Flexible phases in these Borate glasses. These efforts are directed towards better understanding the connection between these phases and glass structure. Here we report preliminary Raman scattering and MDSC results on SrBorates over a wide composition range 0 \textless x \textless 45{\%}, taking special care to synthesize dry and homogeneous melts by induction melting starting materials. Trends in glass transition temperatures T$_{\mathrm{g}}$(x) show a broad maximum (T$_{\mathrm{g}}^{\mathrm{max}} \quad =$ 650\textdegree C) centered near 33 mole{\%} of SrO, and a reversibility window with a width extending from 27.5{\%} to 37.5{\%} and centered about the T$_{\mathrm{g}}^{\mathrm{max}}$ composition. Results on Topological phases in the Sr and Baborates will be compared. \item Vignaroban EPL \item C. Holbrook Ph.D. Thesis (2015). [Preview Abstract] 
Friday, March 17, 2017 1:39PM  1:51PM 
Y16.00013: Correlation study of real delay time and imaginary delay time in 1dimensional weak disorder optical media Peeyush Sahay, Huda M. Almabadi, Prabhakar Pradhan Real delay time ($\tau_{r})$ provides a measure of the time spent by photons inside an optical system. The measurement of $\tau_{r}$ is conducted in terms of energy ($E)$ derivative of the Wigner phase delay ($\varphi )$, as $\tau_{r} =d\phi /dE\propto d\phi /cdk$; $k$ and $c$ represents wavenumber and the speed of light, respectively. The characterization of $\tau_{r}$ requires interferometric system to measure $\varphi $ of the light waves scattering from the medium $[R=\sqrt r \exp (i\phi )$]. We investigated the possibility of extracting the $\tau_{r}$ information from the intensity measurement of the backscattered waves. The study was performed on a 1D model of weak disordered optical system and short sample length by numerically evaluating the backscattered light intensity. An imaginary delay time ($\tau_{i})$, defined as $\tau_{i} =d\theta /cdk$, where $\theta $ represents an `\textit{imaginary phase}', was obtained upon expressing the backscattered intensity as $RR^{\ast }=\vert R\vert^{2}=r=\exp (\theta )$. The result shows a strong correlation between $r$ and $\varphi $; with \quad $\tau _{r}$ and $\tau_{i}$ exhibiting similar statistical distribution but with a shift. The magnitude and variation of the mean and std values of $\tau_{r}$, and the std values of $\tau_{i}$ with sample lengths are nearly the same, which indicates about one parameter theory of delay time. This work potentially paves way for extracting phase information from the intensity distribution without using interferometric systems. [Preview Abstract] 
Friday, March 17, 2017 1:51PM  2:03PM 
Y16.00014: Collective versus singleparticle dynamical fluctuations in a glassforming liquid Rajib Pandit, Elijah Flenner, Horacio E. Castillo We propose a decomposition of the fourpoint dynamic structure factor $S_4(k,t)$ of a glassforming liquid into two contributions: a singleparticle contribution $S_4^{sp}(k,t)$ and a collective contribution $S_4^{coll}(k,t)$. We apply this decomposition to the case of a binary hardsphere mixture in three dimensions. For packing fractions near the glass transition, we find that at times of the order of the alpha relaxation time $\tau_{\alpha}$, the collective contribution can be up to two orders of magnitude larger than the singleparticle one. By contrast, at times two orders of magnitude longer than $\tau_{\alpha}$, the single particle contribution becomes dominant. The collective part can be cleanly extracted at all times, and we use it to study the dynamic correlation length and the collective part of the dynamic susceptibility for timescales up to $100 \tau_{\alpha}$. [Preview Abstract] 
Friday, March 17, 2017 2:03PM  2:15PM 
Y16.00015: Fragility Index variation in (Li$_{2}$O)x(B$_{2}$O$_{3})$100x melts Charles Skipper, Ralph Chbeir, Chandi Mohanty, Punit Boolchand We have measured the fragility index (m) of titled melts as a function of Li$_{2}$O content in the 0\textless x\textless 35{\%} range using Modulated DSC. In this approach, one measures the real and imaginary part of the complex specific heat as a function of modulation frequency ($\nu )$, and deduces an activation energy by plotting the log of the enthalpy relaxation time as a function of inverse Temperature obtained at various $\nu $. For pure B$_{2}$O$_{3}$ glass with a T$_{g} \quad =$ 308\textdegree C, we obtain m $=$ 28 (1). With increasing x, m is found to monotonically increase to 38(1) as x increased to 15{\%}, but then to plateau at a value of m $=$ 42(2) in the range 18{\%}\textless x\textless 25{\%}. These values in m are significantly lower than those reported earlier$^{1}$. In particular, the range of x where we observe a plateau in m, authors of ref. 1 observed a linear increase in the 41\textless m\textless 62 range. T$_{g}$ of our glasses are found to be significantly greater than those of ref. 1, suggesting that the lower value of m in our glasses could be a manifestation of the reduced concentration of bonded water. The range of x across which a plateau is observed also happens to coincide where the isostatically rigid Intermediate Phase reported recently$^{2}$. $^{1}$ G.D.Chryssikos et al. JNCS \textbf{196}, 244 (1996). $^{2}$ K. Vignarooban et al. EPL \textbf{108}, 56001 (2014). [Preview Abstract] 
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