Pyrochlore Oxide Hg2Os2O7 on Verge of Metal–Insulator Boundary

Semimetallic osmium pyrochlore oxide Cd2Os2O7 undergoes a magnetic transition to an all-in-all-out (AIAO)-type order at 227 K, followed by a crossover to an AIAO insulator at around 210 K. Here, we studied the isostructural and isoelectronic compound Hg2Os2O7 through thermodynamic measurements, µSR spectroscopy and neutron diffraction experiments. A similar magnetic transition, probably to an AIAO-type order, was observed at 88 K, while the resistivity showed a decrease at the transition and remained metallic down to 2 K. Thus, the ground state of Hg2Os2O7 is most likely an AIAO semimetal, which is analogous to the intermediate-temperature state of Cd2Os2O7. Hg2Os2O7 exists on the verge of the metal–insulator boundary on the metal side and provides an excellent platform for studying the electronic instability of 5d electrons with moderate electron correlations and strong spin–orbit interactions.

Autobiography of Stanley I. Sandler

I review my career from its academic beginning to my recent retirement. I grew up and studied chemical engineering in New York City. My initial failure to understand thermodynamics the way it had been taught, evidenced by the difficulty I had when starting graduate school, led me years later to write a textbook on the subject that is now in a fifth edition, in addition to other books I have written. My research areas have included molecular simulation, statistical- and quantum mechanical–based methods, and a variety of experimental thermodynamic measurements. In addition, I have been a consultant in traditional chemical engineering areas, as well in nontraditional areas, such as assisting in the design of a heat shield for interplanetary exploration, the destruction of armed chemical weapons, and the cleanup of nuclear weapons production facilities. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 12 is June 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Synthesis and superconductivity of new TiNiSi-type equiatomic germanide ThIrGe

A new germanide ThIrGe has been synthesized and characterized by x-ray diffraction, transmission electron microscopy, electrical resistivity, magnetic susceptibility and thermodynamic measurements. The structural refinement shows that, in contrast to...

Realization of the kagome spin ice state in a frustrated intermetallic compound

Spin ices are exotic phases of matter characterized by frustrated spins obeying local “ice rules,” in analogy with the electric dipoles in water ice. In two dimensions, one can similarly define ice rules for in-plane Ising-like spins arranged on a kagome lattice. These ice rules require each triangle plaquette to have a single monopole and can lead to different types of orders and excitations. Using experimental and theoretical approaches including magnetometry, thermodynamic measurements, neutron scattering, and Monte Carlo simulations, we establish HoAgGe as a crystalline (i.e., nonartificial) system that realizes the kagome spin ice state. The system features a variety of partially and fully ordered states and a sequence of field-induced phases at low temperatures, all consistent with the kagome ice rule.

Spatial Flow-Field Approximation Using Few Thermodynamic Measurements—Part II: Uncertainty Assessments

In this second part of our two-part paper, we provide a detailed, frequentist framework for propagating uncertainties within our multivariate linear least squares model. This permits us to quantify the impact of uncertainties in thermodynamic measurements—arising from calibrations and the data acquisition system—and the correlations therein, along with uncertainties in probe positions. We show how the former has a much larger effect (relatively) than uncertainties in probe placement. We use this non-deterministic framework to demonstrate why the well-worn metric for assessing spatial sampling uncertainty falls short of providing an accurate characterization of the effect of a few spatial measurements. In other words, it does not accurately describe the uncertainty associated with sampling a non-uniform pattern with a few circumferentially scattered rakes. To this end, we argue that our data-centric framework can offer a more rigorous characterization of this uncertainty. Our paper proposes two new uncertainty metrics: one for characterizing spatial sampling uncertainty and another for capturing the impact of measurement imprecision in individual probes. These metrics are rigorously derived in our paper and their ease in computation permits them to be widely adopted by the turbomachinery community for carrying out uncertainty assessments.