arXiv subjects

M. E. Eberhart

Publications and source records attributed to M. E. Eberhart.

4 recordsLinked to original sources

arXiv2021

Neighborhoods and Functionality in Metals

The fundamental construct of organic chemistry involves understanding molecular behavior through functional groups. Much of computational chemistry focuses on this very principle, but metallic materials are rarely analyzed using these techniques owing to the assumption that they are delocalized and do not possess inherent functionality. In this paper, we propose a methodology that recovers functional groups in metallic materials from an energy perspective. We characterize neighborhoods associated with functional groups in metals by observing the evolution of Bader energy of the central cluster as a function of cluster size. This approach can be used to conceptually decompose metallic structure into meaningful chemical neighborhoods allowing for localization of energy-dependent properties. The generalizability of this approach is assessed by determining neighborhoods for crystalline materials of different structure types, and significant structural defects such as grain boundaries and dislocations. In all cases, we observe that the neighborhood size may be universal - around 2-3 atomic diameters. In its practical sense, this approach opens the door to the application of chemical concepts, e.g., orbital methods, to investigate a broad range of metallurgical phenomena, one neighborhood at a time

cond-mat.mtrl-sci↗

arXiv2020

Nearsightedness of Crystalline Materials and Intergranular Embrittlement

Our quest to design materials often envisions as a first step the conceptual decomposition of a material into meaningful atomic scale neighborhoods. The performance of the monolithic material is then seen to arise from the combined properties of these much simpler regions. It is the nearsightedness of electronic matter (NEM) principle that provides the rigorous justification for this "divide and conquer" approach. NEM asserts that a material property may be significantly affected by a perturbation, no matter how large, only over a neighborhood of size $R$. Though NEM posits the existence of meaningful atomic scale neighborhoods, for the most part these regions are identified empirically. In this paper we propose a methodology to divide real materials into meaningful neighborhoods determined by the topology of the charge density. We generalize this approach by applying the same to determine neighborhoods representative of elemental crystalline materials and then use these neighborhoods to model the embrittling effects of bismuth atoms segregated to copper grain boundaries. We show that embrittlement is the result of impurity atom-induced enhancements of copper nearsightedness. We further suggest that just as nearsightedness plays an overlooked role mediating embrittlement, it may also be an important factor affecting a broad range of unresolved problems as apparently diverse as energy focussing phenomena and enzyme kinetics.

cond-mat.mtrl-sci↗

arXiv2020

Observing the 3D chemical bond and its energy distribution in a projected space

Our curiosity-driven desire to "see" chemical bonds dates back at least one-hundred years, perhaps to antiquity. Sweeping improvements in the accuracy of measured and predicted electron charge densities, alongside our largely bondcentric understanding of molecules and materials, heighten this desire with means and significance. Here we present a method for analyzing chemical bonds and their energy distributions in a two-dimensional projected space called the condensed charge density. Bond "silhouettes" in the condensed charge density can be reverse-projected to reveal precise three-dimensional bonding regions we call bond bundles. We show that delocalized metallic bonds and organic covalent bonds alike can be objectively analyzed, the formation of bonds observed, and that the crystallographic structure of simple metals can be rationalized in terms of bond bundle structure. Our method also reproduces the expected results of organic chemistry, enabling the recontextualization of existing bond models from a charge density perspective.

physics.chem-ph↗

arXiv2004

Looking for Design in Materials Design

Despite great advances in computation, materials design is still science fiction. The construction of structure-property relations on the quantum scale will turn computational empiricism into true design.

cond-mat.mtrl-sci↗