There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

Microstructures and properties of high-entropy alloys

The pace of materials discovery for heterogeneous catalysts and electrocatalysts could, in principle, be accelerated by the development of efficient computational screening methods. This would require an integrated approach, where the catalytic activity and stability of new materials are evaluated and where predictions are benchmarked by careful synthesis and experimental tests. In this contribution, we present a density functional theory-based, high-throughput screening scheme that successfully uses these strategies to identify a new electrocatalyst for the hydrogen evolution reaction (HER). The activity of over 700 binary surface alloys is evaluated theoretically; the stability of each alloy in electrochemical environments is also estimated. BiPt is found to have a predicted activity comparable to, or even better than, pure Pt, the archetypical HER catalyst. This alloy is synthesized and tested experimentally and shows improved HER performance compared with pure Pt, in agreement with the computational screening results.

Computational high-throughput screening of electrocatalytic materials for hydrogen evolution

http://ronald-wagner.de/diss/html/lit/share/surfsci411(98)186.pdf

The surface energy of metals

The effect of Al on the 475 degrees C embrittlement of Fe-Cr alloys

Using density-functional theory formulated within the framework of the exact muffin-tin orbitals method, we investigate the stability of the body-centered-cubic phase of Be (beta-Be). The elastic c ...

Structural stability of β-beryllium

We use combined high resolution neutron diffraction (HRPD) with density functional theory (DFT) to investigate the exchange striction at the Curie temperature (${T}_{C}$) of Fe${}_{2}$P and to examine the effect of boron and carbon doping on the P site. We find a significant contraction of the basal plane on heating through ${T}_{C}$ with a simultaneous increase of the $c$ axis that results in a small overall volume change of $\ensuremath{\sim}0.01%$. At the magnetic transition the Fe${}_{I}$-Fe${}_{I}$ distance drops significantly and becomes shorter than Fe${}_{I}$-Fe${}_{II}$. The shortest metal-metalloid (Fe${}_{I}$-P${}_{I}$) distance also decreases sharply. Our DFT model reveals the importance of the latter as this structural change causes a redistribution of the Fe${}_{I}$ moment along the $c$ axis (Fe-P chain). We are able to understand the site preference of the dopants, the effect of which can be linked to the increased moment on the Fe${}_{I}$ site, brought about by strong magnetoelasticity and changes in the electronic band structure.

Magnetoelastic effects in doped Fe2P

By using density-functional theory in combination with the coherent-potential approximation and the disordered local magnetic moment picture, we demonstrate that the competing high-temperature cubi ...

Density-functional study of paramagnetic iron

The Airy gas model is used to derive an expression for the local kinetic energy in the linear potential approximation. The expression contains an explicit Laplacian term $\frac{2}{5}({\ensuremath{\Elzxh}}^{2}/2m){\ensuremath{\nabla}}_{\ensuremath{\mu}}^{2}(\mathbf{r})$ that, according to jellium surface calculations, must be a universal feature of any accurate local description. Applied to the noble gases the expression reduces the errors by a factor of $50$ over previous results obtained by the linear potential approximation.

/pdf/local-kinetic-energy-density-of-the-airy-gas-188ci6gss4.pdf

Levente Vitos

Papers

The effect of Al on the 475 degrees C embrittlement of Fe-Cr alloys

Structural stability of β-beryllium

Magnetoelastic effects in doped Fe2P

Density-functional study of paramagnetic iron

Local kinetic-energy density of the Airy gas