Electronic structure of the sigma-phase in paramagnetic Fe-V alloys. Experimental and theoretical study

The electronic structure of $\sigma$-phase Fe$_{100-x}$V$_x$ compounds with 33.3 $\le x \le 60.0$ was calculated from the charge self-consistent Korringa-Kohn-Rostoker method. For the first time, charge densities $\rho_A(0)$ and electric field gradients were determined at Fe nuclei, that occupy five nonequivalent lattice sites. The highest $\rho_A(0)$ values were found on sites A and D, and the lowest one on site B, the difference ranging between 0.162 and 0.174 $\it s$-like electrons per Fe atom for $x = 33.3$ and $x = 60$, respectively. The calculated quantities combined with experimentally determined site occupancies were successfully applied to analyze $^{57}$Fe M\"ossbauer spectra recorded on a series of 8 samples in a paramagnetic state.Comment: 4 pages, 4 figures, 15 reference

Thematic Design: My Story is Better When Your Story is Better

What does a well-designed thematic workshop look like? Walking into a presentation at a convention center or at a NASA center, one might see formal and informal educators receiving space science content from knowledgeable science experts, actively participating in topic-related activities, questioning, collaborating, and investigating, connecting topics and content to their education needs, and having fun. But what is really going on, and what did it take to get to this point-the point of delivery. This is an opportunity to share experience and knowledge pertaining to designing and conducting space science thematic workshops and trainings. It is an attempt to describe the thematic approach to space science education that has been demonstrated in Solar System Exploration Education Forum workshops over many years and to articulate the best practices pertain-ing to designing and presenting those workshops

Unusual Maternal Dystocia

On October 20, 1941, an eleven-year-old Shorthorn cow was brought into the Stange Memorial Clinic. The owner reported that the cow was bred Jan. 10, 1941, and that it was time for a normal pregnancy to terminate. He also stated that the cow was in labor for several hours

Local distortions of the crystal structure and their influence on the electronic structure and superconductivity of the high-entropy alloy (TaNb)0.67(HfZrTi)0.33

Local distortions of the crystal structure and their influence on the electronic structure, electron-phonon interaction, and superconductivity are theoretically studied in the superconducting high-entropy alloy (HEA) (TaNb)$_{0.67}$(HfZrTi)$_{0.33}$. Distortions of the crystal lattice are caused by the relaxation of atomic positions and are studied in the twelve models of supercells. The largest relative changes in the interatomic distances due to relaxation reach 8\%. On average, local distortions tend to lower the density of states at the Fermi level and significantly reduce the electron-phonon coupling parameter $\lambda$. As a result, the calculated superconducting critical temperature is reduced to about 50\% of the initial value, which shows the strong impact of structural disorder on superconductivity in this prototype high-entropy alloy. With the reduced value of $\lambda$, the theoretical $T_c$ is closer to the experiment for typical values of the Columomb pseudopotential parameter $\mu^*$. The experimental $T_c$ can be reproduced by taking a slightly enhanced $\mu^* = 0.176$, which leaves little room for the possibility of suppression of superconductivity by disorder.Comment: 12 pages, 7 figures + Supplemental Material. Accepted for publication in Physical Review