From Electrons to Finite Elements: A Concurrent Multiscale Approach for Metals

We present a novel methodology to compute relaxed dislocations core configurations, and their energies in crystalline metallic materials using large-scale \emph{ab-intio} simulations. The approach is based on MacroDFT, a coarse-grained density functional theory method that accurately computes the electronic structure but with sub-linear scaling resulting in a tremendous reduction in cost. Due to its implementation in \emph{real-space}, MacroDFT has the ability to harness peta...

In conventional fluid mechanics, the chemical composition and thermodynamic state of a fluid-solid interface are not considered when establishing velocity-field boundary conditions. As a consequence, fluid simulations are usually not able to generate different outputs when interfacial materials are varied. By considering an atomistic description of matter, theoretical determination of material-specific boundary conditions becomes possible, thereby providing an improved altern...

A comparative study of fracture in Al is carried out by using quantum mechanical and empirical atomistic description of atomic interaction at crack tip. The former is accomplished with the density functional theory (DFT) based Quasicontinuum method (QCDFT) and the latter with the original Quasicontinuum method (EAM-QC). Aside from quantitative differences, the two descriptions also yield qualitatively distinctive fracture behavior. While EAM-QC predicts a straight crack front...

In this research, atomistic molecular dynamics simulations are combined with mesoscopic phase-field computational methods in order to investigate phase-transformation in polycrystalline Aluminum microstructure. In fact, microstructural computational modeling of engineering materials could help to optimize their mechanical properties for industrial applications (e.g. directional solidification for turbine blades). As a result, a multiscale modeling approach is developed to fin...

Through millennia humans exploited the natural property of metals to get stronger or hardened when mechanically deformed. Ultimately rooted in the motion of dislocations, mechanisms of metal hardening remained in the crosshairs of physical metallurgists for over a century. Here, we performed atomistic simulations at the limits of supercomputing, which are sufficiently large to be statistically representative of macroscopic crystal plasticity yet fully resolved to examine the ...

The design of next-generation alloys through the Integrated Computational Materials Engineering (ICME) approach relies on multi-scale computer simulations to provide thermodynamic properties when experiments are difficult to conduct. Atomistic methods such as Density Functional Theory (DFT) and Molecular Dynamics (MD) have been successful in predicting properties of never before studied compounds or phases. However, uncertainty quantification (UQ) of DFT and MD results is rar...

In this paper we present a modeling approach to bridge the atomistic with macroscopic scales in crystalline materials. The methodology combines identification and modeling of the controlling unit processes at microscopic level with the direct atomistic determination of fundamental material properties. These properties are computed using a many body Force Field derived from ab initio quantum-mechanical calculations. This approach is exercised to describe the mechanical respons...

Quantum nanosystems involve the coupled dynamics of fermions or bosons across multiple scales in space and time. Examples include quantum dots, superconducting or magnetic nanoparticles, molecular wires, and graphene nanoribbons. The number (10^3 to 10^9) of electrons in assemblies of interest here presents a challenge for traditional quantum computations. However, results from deductive multiscale analysis yield coarse-grained wave equation that capture the longer-scale quan...

Atomistic theory holds the promise for the ab initio development of superalloys based on the fundamental principles of quantum mechanics. The last years showed a rapid progress in the field. Results from atomistic modeling enter larger-scale simulations of alloy performance and often may be compared directly to experimental characterization. In this chapter we give an overview of atomistic modeling and simulation for Ni-base superalloys. We cover descriptions of the interatom...

Nanoindentation is a powerful tool capable of providing fundamental insights of material elastic and plastic response at the nanoscale. Alloys at nanoscale are particularly interesting as the local heterogeneity and deformation mechanism revealed by atomistic study offers a better way to understand hardening mechanism to build a stronger material. In this work, nanoindentation in Al-Cu alloys are studied using atomistic simulations to investigate the effects of loading direct...