https://escholarship.org/content/qt5r15b762/qt5r15b762.pdf?t=p2aswe

The stability and structure of high miller index platinum crystal surfaces in vacuum and in the presence of adsorbed carbon and oxygen

The theory of the electronic structure of clean metal and semiconductor surfaces is reviewed, starting from an effective one-electron Schrodinger equation. Methods for solving the Schrodinger equation at surfaces are briefly described, and the effects of the surface on the electronic wavefunctions are discussed using simple models. The results of detailed calculations of the surface electronic structure of s-p bonded metals, transition metals and semiconductors are reviewed, with an emphasis on the effect of the local environment on the density of states. Properties like the work function and surface energy depend on the surface electronic structure, and their variation with material and surface is discussed; the surface energy contains an important contribution from the interaction between electrons, and this will be considered in some detail. The change in electronic structure compared with the bulk leads to changes in atomic structure, with surface reconstruction on semiconductor and some metal surfaces, and this is also discussed. The interplay between theory and experiment is very important in surface studies, and the theoretical surface energy bands reviewed compare well with experimental photoemission results; this comparison has proved particularly useful for understanding surface reconstructions.

https://iopscience.iop.org/article/10.1088/0034-4885/45/3/001/pdf

Surface electronic structure

Atomistic simulations such as molecular dynamics and Monte Carlo are widely used for understanding the material behavior at a more fundamental level, e.g., at the atomic level. However, there still exist limitations in the variety of material systems, specimen size and simulation time. This article briefly outlines the formalism and performance of the second nearest-neighbor modified embedded-atom method, an interatomic potential formalism applicable to a wide range of materials systems. Recent progresses made to overcome the inherent size and time limitations of atomistic simulations are also introduced along with the challenges still remaining in extending their applicability. Finally, the authors release all the potential parameter sets for elements and alloy systems, and relevant homemade atomistic simulation codes based on the interatomic potential formalism with a user guide.

The modified embedded-atom method interatomic potentials and recent progress in atomistic simulations

Atom probe field ion microscopy of a FeNiB glass

In this study, we compute grain boundary (GB) properties for a large set of GBs in bcc transition metals with a special focus on W, Mo and Fe using ab initio density functional theory (DFT) and semi-empirical second nearest neighbour modified embedded atom method (2NN-MEAM) potentials. The GB properties include GB energies, surface energies, GB excess volume and work of separation, which we analyse and then compare to experimental data. We find that the used 2NN-MEAM potentials can predict general trends of GB properties, but do not always reproduce the GB ground state structure and energy found with DFT. In particular, our results explain the experimental finding that W and Mo prefer intergranular fracture, while other bcc metals prefer transgranular cleavage.

/pdf/ab-initio-calculations-of-grain-boundaries-in-bcc-metals-4xqt3rj1ut.pdf

Ab initio calculations of grain boundaries in bcc metals

Surface energy anisotropy of iron

Surface energy anisotropy of iridium

Surface energy anisotropy of tungsten

Field-ion microscope investigations of fine structures in as-quenched and tempered ferrous martensite

Hydrogen-ion microscopy has been used to study microstructural features of tempered martensite in a commercial FeO8% C-0·4% Mn steel, and a comparison between microstructure and measured microhardness has been made. At peak hardness in the early first stage of tempering, a high density of carbides with {100} habits and primarily in the form of very thin platelets is present. Many of these particles are coherent and some are associated with dislocations. As the hardness decreases, the density of particles decreases and their length and width increase rapidly. Their thickness, however, increases very slowly and coherency is maintained for a large number of particles throughout the first stage of tempering. In the late first stage of tempering large incoherent carbide platelets with {112} and {110} habits begin to form; and in the third stage of tempering where the hardness drops more rapidly, a comparatively low density of these large incoherent carbides is found. These results support the theory t...

Helen E. Grenga

Papers

Surface energy anisotropy of iron

Surface energy anisotropy of iridium

Surface energy anisotropy of tungsten

Field-ion microscope investigations of fine structures in as-quenched and tempered ferrous martensite

Field-ion microscopy of tempered martensite