Uncertainty Quantification in Atomistic Modeling of Metals and Its Effect on Mesoscale and Continuum Modeling: A Review.

The design of next-generation alloys through the integrated computational materials engineering (ICME) approach relies on multiscale 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 rarely reported due to computational and UQ methodology challenges. Over the past decade, studies that mitigate this gap have emerged. These advances are reviewed in the context of thermodynamic modeling and information exchange with mesoscale methods such as the phase-field method (PFM) and calculation of phase diagrams (CALPHAD). The importance of UQ is illustrated using properties of metals, with aluminum as an example, and highlighting deterministic, frequentist, and Bayesian methodologies. Challenges facing routine uncertainty quantification and an outlook on addressing them are also presented.

Interface-Driven Structural Distortions and Composition Segregation in Two-Dimensional Heterostructures.

The discovery of emergent phenomena in 2D materials has sparked substantial research efforts in the materials community. A significant experimental challenge for this field is exerting atomistic control over the structure and composition of the constituent 2D layers and understanding how the interactions between layers drive both structure and properties. While no segregation for single bilayers was observed, segregation of Pb to the surface of three bilayer thick PbSe-SnSe alloy layers was discovered within [(Pbx Sn1-x Se)1+δ ]n (TiSe2 )1 heterostructures using electron microscopy. This segregation is thermodynamically favored to occur when Pbx Sn1-x Se layers are interdigitated with TiSe2 monolayers. DFT calculations indicate that the observed segregation depends on what is adjacent to the Pbx Sn1-x Se layers. The interplay between interface- and volume-free energies controls both the structure and composition of the constituent layers, which can be tuned using layer thickness.