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Materials Day 2006 - Posters

Computer Simulation and Modeling

• B07 - Computational Phase Transformations and Microstructure Evolution
  L. Q. Chen
  Abstract: Many engineering materials are designed by controlling their phase transformations and microstructure evolution. Examples include the improvement of mechanical properties through precipitation reactions in Ni-based superalloys and age-hardened Al-alloys and the useful dielectric properties and electro-mechanical coupling effects by manipulating the phase transitions in ferroelectric crystals. The primary focus of Professor ChenÆs group for the last decade has been on developing computational models for predicting the kinetics of phase transformations and microstructure evolution. In particular, his group has developed a series of phase-field models for various materials processes including grain growth,precipitate reactions, domain formation, particle coarsening, ferroelectric phase transitions and domain structure evolution in thin films, domain evolution in ferromagnetic shape memory alloys, dislocation-precipitate interactions, and morphological stability of nanoscale thin films.
  
  
• B08 - Computational Tools for Ni-Base Superalloys
  T. Wang, Y. Wang, J. Z. Zhu, S. H. Zhou, R. A. MacKay, Z.-K. Liu, L. Q. Chen
  Abstract: A set of integrated computational tools have been developed for predicting the thermodynamics and microstructure evolution in Ni-base superalloys. The thermodynamic, kinetic and lattice parameter databases for the Ni-Al-Mo-Ta quaternary system were developed with first-principles results and experimental data in the literature as inputs. A quantitative phase-field model for predicting the 3D microstructure evolution of Gamma prime precipitates is developed. A comparison between experimental measurements and phase-field simulations show excellent agreement in precipitate morphology, coarsening kinetics, and precipitate size distributions in both time and length scales.
  
  
• B09 - Phase-Field Microelasticity Theory and Micromagnetic Simulations of Domain Structures in Giant Magnetostrictive Materials
  J. X. Zhang, L. Q. Chen
  Abstract: A computational model is proposed to predict the stability of magnetic domain structures and their temporal evolution in giant magnetostrictive materials by combining a micromagnetic model with the phase-field microelasticity theory of Khachaturyan. The model includes all the important energetic contributions, including the magnetocrystalline anisotropy energy, exchange energy, magnetostatic energy, external field energy, and elastic energy. Both Fe81.3Ga18.7 and Terfenol-D are considered as examples. The effects of elastic energy and magnetostatic energy on domain structures were studied. The magnetostriction and associated domain structure evolution under an applied field were modeled under different pre-stress conditions. It is shown that a compressive pre-stress can efficiently increase the overall magnetostrictive effect. The results are compared with existing experiment measurements and observations.
  
  
• B10 - A New Algorithm for the Automation of Phase Diagram Calculation
  M. Emelianenko, Z.-K. Liu, Q. Du
  Abstract: We propose a new scheme to optimize the phase diagram construction algorithm adopted in ThermoCalc. New method possesses advantages over existing methods in terms of speed and computational complexity and can be used to automate the calculation of phase equilibria in complex multicomponent systems.
  
  URL: http://www.matcase.psu.edu
  
  
• B11 - Molecular Dynamics Simulation of Interaction of Energetic C60 molecules with Water Ice
  I. Wojciechowski, B. J. Garrison
  Abstract: Investigation of secondary particle emission from weakly bonded solids under bombardment by energetic clusters is of interest due to a number of applications. Frozen-gas matrixes with embedded organic molecules are used in secondary ion mass spectrometry experiments. In these experiments, the bombardment causes the molecules and/or their fragments to release from the matrix into the gas phase where they are available for the analysis. Another application is connected with the fact that many objects in the outer solar system (giant planetsÆ moons, comets) are covered with (or consist of) ices. Products of the surface erosion caused by the particles from the planet rings can provide the information about the object evolution and composition. To understand the physics of the processes involved we performed molecular dynamics simulations to model the bombardment of water ice by energetic C60 projectiles. The emission process is demonstrated to exhibit the process of expansion of the superheated gas into vacuum.
  
  
• B12 - Generation of OH Radical from Fractured Silica Surfaces: Implications for Silica-Induced Lung Cancer
  J. D. Kubicki, J. Narayan
  Abstract: Interactions between inorganic surfaces and biological compounds are important for in lung diseases caused by mineral dusts (e.g. silicosis). This poster focuses on research that illustrates the applicability of ab initio computational methods for understanding bioinorganic chemistry. The model calculations presented here examine various methods of how super-oxide and/or hydroxide radicals can be generated on broken silica surfaces. One hypothesis regarding the negative health effects of silica in the lungs is that radicals are formed on the particle surface that attack DNA or other compounds. Comparisons of the potential energies for the ionic and radical states created after the breakage of an Si-O-Si linkage are made based on B3LYP and MP2 calculations. The interactions of H2O and O2 with these model surface defects sites are also modeled. Radical states are predicted to be more stable, and the interaction of H2O with the SiO radical is predicted to generate OH radicals.
  
  URL: http://www.geosc.psu.edu/envchem/
  
  
• C01 - National Science Foundation Industry/University Cooperative Research Center on Computational Materials Design (NSF I/UCRC CCMD)
  Z.-K. Liu, D. McDowell
  Abstract: The CCMD aims to promote research programs of interest to both industry and university, to educated a new generation of scientists and engineers with a broad, industrially oriented perspective on engineering research and practice, to enhance the infrastructure of computational materials research in the nation, to explore and extend the interface between engineering systems design, information technology and physics-based simulation of process-structure and structure-property relations of materials, and to improve the intellectual capacity of the workforce through industrial participation, high quality research projects, and development of curriculum in computational and systems design aspects of materials. This will be achieved by developing long-term partnerships among industry, university and other organizations in both research and educational aspects. The temporary CCMD web site is http://phases.metcse.psu.edu/ccmd and the future CCMD web site is http://www.ccmd.psu.edu.
  
  URL: http://phases.metsce.psu.edu/ccmd
  
  
• C02 - System Materials Design: First Principle Calculations, Computational Thermodynamics and Phase Transformations
  Z.-K. Liu
  Abstract: The Phases Research Lab in the Department of Materials Science and Engineering at Penn State conducts research on the thermodynamics and kinetics of many different material systems to offer an overall system approach to materials design. Research covers properties on atomic level through to macroscopic properties on bulk experimental alloys. On-going projects include: System materials design of magnesium alloys; Hydrogen storage materials; Perovskites; Effects of impurities on process of Al alloys; Alloy design of spray formed Al-Y-Ni-Co alloys; Computational tools for Ni-based superalloys; System alloy design of Pt-based alloys; Modeling of CVD reactions; NSF Information Technology Research; Computational tools for multi-component material design.
  
  URL: http://phases.metsce.psu.edu
  
  
• C03 - Ab initio Molecular Dynamics Simulation of Proton Transfer Mechanism in Hydrated Nafion System
  A. Chaudhari, J. O. Sofo
  Abstract: Proton transfer in hydrated polymer systems is the key microscopic mechanism to understand conductivity in proton exchange fuel cell membranes. We perform ab initio molecular dynamics simulations of a model Nafion/Water system to determine the characteristics of this process, the effect of counter ion density, and its influence in the overall transport mechanisms. Our simulations show the Grotthuss mechanism of proton transfer in water. Protons diffuse through a series of hydronium ion formation and dissociation mediated by Znndel ions. For polymers with a high density of sulfonic groups we obtained a hydronium average lifetime of 112 fsec. The orientation of water molecules forced by the solvation of the counterions interferes with the proper alignment that facilitates proton transfers. We calculate the diffusion coefficient of the instantaneous center of excess charge to estimate the conductivity of these systems.
  
  URL: http://www.phys.psu.edu/~sofo