Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session S21: Materials at Extremes: Kinetics of Phase TransitionsFocus
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Sponsoring Units: GSCCM DCOMP DMP Chair: Ricky Chau, LLNL Room: 320 |
Thursday, March 17, 2016 11:15AM - 11:27AM |
S21.00001: Coupling phase transition kinetics and hydrodynamics: Models for solid-solid and liquid-solid transformation in dynamically driven materials Jonathan Belof, Lorin Benedict, Alexander Chernov, Burl Hall, Sebastien Hamel, Tomorr Haxhimali, Babak Sadigh, Luis Zepeda-Ruiz High pressure and high strain-rate experiments are opening a new frontier toward the study of material science under extreme conditions. As the energy density of experimental platforms is increased, the timescale for observation is typically decreased to the point where the time dependence of phase transitions is now a subject of direct study. We will present new phase transition kinetics models that have been developed with unique considerations that arise in shock-wave driven phase transformation, highlighting applications of the methodology to the simulation of recent experiments of iron and water. [Preview Abstract] |
Thursday, March 17, 2016 11:27AM - 11:39AM |
S21.00002: Construction of a kinetics model for liquid-solid transitions built from atomistic simulations Lorin Benedict, Luis Zepeda-Ruiz, Tomorr Haxhimali, Sebastien Hamel, Babak Sadigh, Alexander Chernov, Jonathan Belof We discuss work in progress towards a kinetics model for dynamically-driven liquid-solid transitions built from MD simulations. The growth of solid particles within a liquid is studied for a range of conditions, and careful attention is paid to the construction of an accurate multi-phase (equilibrium) equation of state for the system under consideration, in order to provide a framework upon which the non-equilibrium physics is based. [Preview Abstract] |
Thursday, March 17, 2016 11:39AM - 11:51AM |
S21.00003: A mean-field thermodynamic description of the kinetics of overdriven interfaces. Tomorr Haxhimali, Jonathan Belof, Babak Sadigh A key aspect of an accurate description of shock-induced structural phase transitions is the rigorous computation of the dynamics of the interfaces between coexisting phases. In the wake of the shock, the system will be exposed to strong gradient fields that give rise to overdriven interfaces during the induced phase transformation. In this work we take a mean-field approach using a time-dependent Ginzburg-Landau formalism to describe the dynamics of such overdriven interfaces. We make a connection of the mean-field result to a quasi-Langevin description, the Kardar-Parisi-Zhang (KPZ) equation, of the kinetics of the interface. Further, larger coarse-grained descriptions of the phase transition such as the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model, which are commonly coupled to hydrodynamic equations that describe the evolution of the temperature and pressure during the shock propagation, ignore the details of the dynamics and structure of the interfacial regions. Overlaying the KPZ description of the interface evolution to these coarse-grained methods will result in physically more accurate multiscale models for shock propagation. We will present results from our efforts in this regard. [Preview Abstract] |
Thursday, March 17, 2016 11:51AM - 12:27PM |
S21.00004: Dynamic materials response at multiscales: Experiments and simulations Invited Speaker: Sheng-Nian Luo One of the grand challenges in materials physics is dynamic responses to impulsive loading, including shock waves, radiation, and pulsed fields, due to their highly transient nature and extremely complex microstructure effects. Dynamic responses, such as plasticity, damage, cavitation, phase changes, and chemical reactions, are inherently multiscale and heavily dependent on microstructure. One has to resort to a suite of tools, including experiments, modeling and simulations, and theory. However, the gaps in spatial or temporal scales between experiments and simulations are still wide, while cross-scale theories are still in early development. To this end, we exploit large-scale molecular dynamics simulations, electron microscopy, and ultrafast synchrotron X-ray imaging and scattering, to probe materials response at length scales ranging from lattice to micron, and time scales, from picosecond to second. For examples, simultaneous, high-speed, X-ray imaging (mesoscale strain-field mapping) and diffraction measurements along with macroscopic measurements have been achieved. Based on classical nucleation theory and large-scale molecular dynamics simulations, we demonstrate the equivalence between length and time scales for nucleation events, which provides a framework to bridge different scales. Certainly, advancing multiscale science requires sustained, concerted, experimental, modeling and theoretical efforts. [Preview Abstract] |
Thursday, March 17, 2016 12:27PM - 12:39PM |
S21.00005: Accelerating Molecular Dynamics Simulations to Investigate Shock Response at the Mesoscales. Avinash Dongare, Garvit Agarwal, Ramakrishna Valisetty, Raju Namburu, Arunachalam Rajendran The capability of large-scale molecular dynamics (MD) simulations to model dynamic response of materials is limited to system sizes at the nanoscales and the nanosecond timescales. A new method called quasi-coarse-grained dynamics (QCGD) is developed to expand the capabilities of MD simulations to the mesoscales. The QCGD method is based on solving the equations of motion for a chosen set of representative atoms from an atomistic microstructure and retaining the energetics of these atoms as would be predicted in MD simulations. The QCGD method allows the modeling of larger size systems and larger time-steps for simulations and thus is able to extend the capabilities of MD simulations to model materials behavior at mesoscales. The success of the QCGD method is demonstrated by reproducing the shock propagation and failure behavior of single crystal and nanocrystalline Al microstructures as predicted using MD simulations and also modeling the shock response and failure behavior of Al microstructures at the micron length scales. The scaling relationships, the hugoniot behavior, and the predicted spall strengths using the MD and the QCGD simulations will be presented. This work is sponsored by the US Army Research Office under Contract{\#} W911NF-14-1-0257. [Preview Abstract] |
Thursday, March 17, 2016 12:39PM - 12:51PM |
S21.00006: Corrections of Hayes Equation of State for Phase Transform under Dynamic Loading. Tao Chong \textbf{Abstract}: The experimental results of iron under ramp wave and shock compression are simulated with Hayes equation of state (EOS) for phase transition. The calculated results are consistent with the experimental data under shock, and don't agree well with the data under ramp wave loading. The reason for the problem is that the bulk modulus in Hayes model is constant (i.e., Bulk sound speed is constant). The sound speed corresponds to the slope of the Rayleigh line when materials leap from the initial state to the final state under shock loading, therefore, the bulk modulus can be considered as a constant. However, under ramp loading, material from initial to the final state is consecutive, and the bulk modulus is not a constant any more but a function of pressure and temperature. The bulk modulus of Hayes EOS is corrected with Murnaghan EOS, and the corrected Hayes EOS is applies to simulate the experimental results. The results show that the calculated data agree well with the experimental data under both shock and ramp wave loadings. . [Preview Abstract] |
Thursday, March 17, 2016 12:51PM - 1:03PM |
S21.00007: Mercury Induced by Pressure to act as a Transition Metal in Mercury Fluorides Jorge Botana, Xiaoli Wang, Chunju Hou, Dadong Yan, Haiqing Lin, Yanming Ma, Mao-Sheng Miao The question of whether Hg is a transition metal remains open for stable solids. In our work we propose that high-pressure techniques will help prepare unusual oxidation states[1] of Hg in Hg-F compounds. By means of \textit{ab initio} calculations and an advanced structure-search algorithm we find that under high pressure charge is transferred from the Hg d orbitals to the F, and becomes a transition metal.[2] HgF$_3$ and HgF$_4$ have been found to be stable compounds at high pressure. HgF$_4$ consists of planar molecules, a typical geometry for d$^8$ metallic centers. HgF$_3$ is an example of metallic and ferromagnetic compound, with an electronic structure analogous to transparent conductors due to the Hg d$^9$ configuration. \begin{thebibliography}{} \bibitem{csf} M.-S. Miao, Nat. Chem. \textbf{5}, 846 (2013) \bibitem{hgf} J. Botana, X. Wang, C. Hou, D. Yang, H. Lin, Y. Ma, M.-S. Miao, Angew. Chem. Int. Edit. \textbf{54}, 9280 (2015). \end{thebibliography} [Preview Abstract] |
Thursday, March 17, 2016 1:03PM - 1:15PM |
S21.00008: Can high pressure I-II transitions in semiconductors be affected by plastic flow and nanocrystal precipitation in phase I? B. A. Weinstein, G. P. Lindberg Pressure-Raman spectroscopy in ZnSe and ZnTe single crystals reveals that Se and Te nano-crystals (NCs) precipitate in these II-VI hosts for pressures far below their I-II phase transitions.[1] The inclusions are evident from the appearance and negative pressure-shift of the A1 Raman peaks of Se and Te (trigonal phase). The Se and Te NCs nucleate at dislocations and grain boundaries that arise from pressure-induced plastic flow. This produces chemical and structural inhomogeneities in the zincblende phase of the host. At substantially higher pressures, the I-II transition proceeds in the presence of these inhomogenities. This can affect the transition's onset pressure P$_{t}$ and width $\Delta $P$_{t}$, and the occurrence of metastable phases along the transition path. Precipitation models in metals show that nucleation of inclusions depends on the Peierls stress $\tau _{p}$ and a parameter $\alpha $ related to the net free energy gained on nucleation. For favorable values of $\tau_{p}$ and $\alpha $, NC precipitation at pressures below the I-II transition could occur in other compounds. We propose criteria to judge whether this is likely based on the observed ranges of $\tau_{p}$ in the hosts, and estimates of $\alpha $ derived from the cohesive energy densities of the NC materials. One finds trends that can serve as a useful guide, both to test the proposed criteria, and to decide when closer scrutiny of phase transition experiments is warranted, e.g., in powders where high dislocation densities are initially created. [1] G. P. Lindberg, et. al., Phys. Status Solidi B 250, 711 (2013) [Preview Abstract] |
Thursday, March 17, 2016 1:15PM - 1:27PM |
S21.00009: Tin phase transition in terapascal pressure range described accurately with Quantum Monte Carlo. Roman Nazarov, Randolph Hood, Miguel Morales The accurate prediction of phase transitions is one of the most important research areas in modern materials science. The main workhorse for such calculations, Density functional theory (DFT), employs different forms of approximate exchange-correlation functionals which may lead to overstabilization of one phase compared to another, therefore, predict incorrectly phase transition pressures. A recent example of such deficiency has been demonstrated in Sn: no bcc to hcp phase transition has been observed in Sn when dynamically compressed to 1.2 TPa while DFT predicts a transition to occur at 0.16-0.2 TPa [1]. To overcome the limitations of DFT, we have employed diffusion quantum Monte Carlo (DMC) method which treats the many body electron problem directly. In order to get highly accurate results we systematically assess the effect of controllable approximations of DMC such as fixed node approximation, finite-size effects and the use of pseudopotentials. Based on metrologically accurate DMC equation of states we construct the pressure-temperature phase diagram and demonstrate its good agreement with experiment in contrast to DFT calculations. [1] A. Lazicki et al., X-Ray Diffraction of Solid Tin to 1.2 TPa. Phys. Rev. Lett. 115, 075502 (2015). [Preview Abstract] |
Thursday, March 17, 2016 1:27PM - 1:39PM |
S21.00010: Phase conversion in silicon and carbon nanomaterials at extreme pressure Matthew Crane, Bennett Smith, Evan Abramson, Peter Pauzauskie The high pressures and temperatures accessible in laser-heated diamond anvil cells (LH-DAC) have produced fundamental insights by identifying metastable states with extraordinary properties. However, the actual conditions necessary to access a metastable state depend on the kinetics of phase transformation. The explosion of research in nanomaterials has generated interest in exploring how phase transformations occur in materials with high radii of curvature, and how we can leverage these effects. We present work investigating phase transformations in Si- and C-based nanomaterials with high radii of curvature. We have loaded a LH-DAC with Si nanowires (NWs) and examined the phase at a range of pressures to discover a recoverable phase transition to a wurtzite crystal structure. For C materials, we have synthesized a pyrolyzed carbon aerogel, an amorphous carbon sol gel with size features of \textasciitilde 10 nm and incredibly low density and thermal conductivity (\textasciitilde 10$^{\mathrm{-2}}$ W/m-K). We investigate spatial resolution of heating under pressure and the effect of temperature on resulting material electronic structure. Finally, we model heating with Mie theory to provide insights into the phase transformations of nanomaterials. [Preview Abstract] |
Thursday, March 17, 2016 1:39PM - 1:51PM |
S21.00011: ABSTRACT WITHDRAWN |
Thursday, March 17, 2016 1:51PM - 2:03PM |
S21.00012: Equilibrium phase boundary between hcp-cobalt and fcc-cobalt Hyunchae Cynn, Magnus J. Lipp, William J. Evans, Bruce J. Baer In 2000 (Yoo et al., PRL), fcc-cobalt was reported as a new high pressure phase transforming from ambient hcp-cobalt starting at around 105 GPa and 300 K. Both cobalts coexist up to 150 GPa and thereafter only fcc-cobalt was found to be the only stable phase to 200 GPa. Our recent synchrotron x-ray diffraction data on cobalt are at odds with the previous interpretation. We will present our new finding and elaborate on our understanding in terms of the equilibrium phase boundary of cobalt. We will also compare our previous work on xenon (Cynn et al., 2001, PRL) with our new results on cobalt. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Portions of this work were performed at HPCAT (Sector 16), APS, Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DENA0001974 and DOE-BES under Award No. DE-FG02-99ER45775. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Thursday, March 17, 2016 2:03PM - 2:15PM |
S21.00013: Atomistic simulation of Shock Induced Structural Phase Transition of Single Crystal Copper Nilanjan Mitra, Anupam Neogi It is well known that pure Single crystal copper subjected to shock wave loading of different intensities results in development of different types of plasticity mechanisms. Beyond that regime of shock wave intensity it has also been shown in several literature that single crystal Cu shows melting. A regime of shock loading has been identified in this research in which single crystal Cu undergoes a structural phase transition. Identification of this structural phase transition mechanism as well as the resulting phase has not only been done using radial distribution functions and structure factor but also with virtual X-Ray diffraction. Phonon dispersion at these high temperatures and pressures have also been investigated. The effect of crystallographic orientation and initial temperature of the sample has been investigated in this simulation study. [Preview Abstract] |
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