Computational Approaches to Materials for Energy Applications: Session I
Sponsored by: TMS Extraction and Processing Division, TMS Light Metals Division, TMS: Energy Committee
Program Organizers: Laurent Chaput, LEMTA

Wednesday 8:30 AM
March 1, 2017
Room: 7A
Location: San Diego Convention Ctr

Session Chair: Laurent Chaput, Lorraine University

8:30 AM  Invited
Visual Search Strategies for Thermoelectrics: David Singh1; 1University of Missouri
    Thermoelectric performance depends on a contraindicated combination of transport properties. In particular, it requires high conductivity, high thermopower and low thermal conductivity. The contradiction implied by the need for both high thermopower and high conductivity implies that excellent thermoelectric materials should have unusual electronic structures that are not described by simple isotropic parabolic band models. This talk presents a discussion of the unusual electronic features that can lead to high thermoelectric performance and search strategies for identifying candidate materials.

9:00 AM  Invited
First Principles Calculations of the Stability and Physical Properties of Thermoelectric Materials: Philippe Jund1; Kinga Niedziolka1; Alexandre Berche1; Patrick Hermet1; Jean-Claude TÚdenac1; 1ICGM-Montpellier University
     Adaptation of thermoelectric materials to industrial applications demands to design relatively complex materials. The search and optimization of these materials requires not only to have an in depth knowledge of their thermoelectric properties but also of other physical properties such as their mechanical and thermodynamical stability often linked to the presence of structural defects. Experimentally the study of these properties can often not be performed exhaustively and is sometimes difficult to tackle especially concerning the defects. This is where first principles calculations can be of a precious help especially in permitting to select better materials in silico before going to the synthesis. In this presentation we will illustrate the input of these calculations on three aspects of the design of a material: - the influence of defects/dopants on the thermoelectric properties, - the phase stability and best adapted synthesis routes, - the thermal properties and in particular the thermal conductivity

9:30 AM  Invited
Accelerated Discovery of Novel Low-thermal-conductivity Crystals by First-principles Data-driven Approach: Isao Tanaka1; 1Kyoto University
    An approach called “virtual screening” uses a machine-learning technique to estimate the target property. After screening the whole library, verification process is required to examine the predictive power of the model. Models can be improved iteratively through Bayesian optimization process. The virtual screening is useful when real screening is not practical, i.e. when the production cost for the descriptors is too high to cover the whole library within the practical time. This is the same if one needs to explore too large space to cover exhaustively. Discovery of new low lattice-thermal-conductivity (LTC) crystals through the virtual screening technique will be shown as an example. We have established our own dataset of LTC computed by the first principles anharmonic force constant method as implemented in phonopy, an open source package for first principles phonon calculations. Candidates found by the virtual screening are validated by first principles LTC calculations.

10:00 AM Break

10:20 AM  Invited
Monte Carlo Modeling of Phonon Transport in Nanostructures: David Lacroix1; 1University of Lorraine
    Monte Carlo (MC) modeling has proven to be an accurate and efficient technique to deal with many physics, chemistry and engineering problems. It has successfully adapted to solve the Boltzmann Transport Equation for phonons. In the latter case, heat propagation in nanostructured materials like nanofilms, nanowires or phononic crystals can be addressed accurately. With this technique, thermal conductivity, Kapitza resistance and thermal conductance can be appraised as long as phonon dispersions and relaxation times are known. This is the case for major semiconducting materials but becomes no longer true with complex compounds where such data are unavailable or partial. To answer this challenge we propose a new multiscale approach which joins DFT calculations to MC modeling. Using ab-initio techniques accurate material bulk phonon properties can be appraised. They are the input of an improved MC tool which is used to model the thermal properties of nanostructures made of complex compounds.

10:50 AM  
Tuning Thermal Conductivity of Metal-Organic–Frameworks: Luping Han1; Wenxi Huang1; Agnieszka Truszkowska1; P. Greaney2; 1OSU; 2UCR
    Metal-organic framework materials (MOFs) are nanoporous materials with amazing potential for application in vehicular hydrogen storage systems. However, the poor thermal conductivity of the adsorption bed (MOFs) in the systems limits their gas storage utility. Central to the performance of the MOF is its ability to withdraw heat from the absorbed working gas. Our research is to understand the fundamental processes of heat transport both within MOF-5 and across interfaces between grains of MOF-5. Here we show that intercalating a gas into the framework of MOF-5 can produce a more than 25-fold increase in the MOF’s thermal conductivity, although the gas itself is condensed on the framework and carries little heat. Analysis of the MOF’s vibrational spectrum shows that the intercalated gas adds vibrational coupling in the framework. These result suggest exciting mechanisms for externally tuning thermal conductivity in these materials. Acknowledgments: NSF, ACS PRF and XSEDE.

11:10 AM  Cancelled
Atomistic Study of the Synergistic Effects of Helium and Hydrogen Bubbles in Nickel: Edmanuel Torres1; Colin Judge1; Jeremy Pencer1; Lori Walters1; 1Canadian Nuclear Laboratories
    Synergistic effects between hydrogen and helium solutes in nickel have been observed in experiments. The detrimental structural change has been associated with enhancement of bubble size and swelling rate when both elements are present. However, the synergistic effects are still not well understood. It is still not conclusive whether they play a critical role in material performance. Nickel-bearing alloys are used in fission nuclear reactors and are expected in fusion reactors. Therefore, an understanding of the synergistic interactions between helium and hydrogen and their role in structural changes in nickel is needed for prediction in materials performance. We perform a combined density functional theory (DFT) and molecular dynamics study of hydrogen and helium clusters and bubbles in nickel, to determine the synergistic mechanisms behind bubble formation. Large scale molecular dynamics simulations based on developed classical potentials are performed to study the combined behavior of H and He in nickel.