The flux-switching transverse flux permanent magnet linear machine (FSTFPMLM) is proposed in this paper combining the advantages of transverse flux linear machine and flux-switching linear machine. Firstly, the structure and operating principle of FSTFPMLM is presented. Secondly, the magnetic field of a simplified FSTFPMLM is numerically computed by three-dimensional (3-D) finite element method (FEM). Thirdly, the thrust characteristics of the machine, including thrust force, cogging force and force ripple are numerically analyzed. The influence of structure parameters on the thrust characteristics has been analyzed by 3-D FEM. The law of thrust, cogging force and force ripple as the pole pitch ratio between primary and secondary and the ratio between tooth width and pole pitch of secondary variable provides the guidance to design FSTFPMLM, which aims to achieve the larger thrust, smaller cogging and force ripple using less permanent magnet materials. The thrust force capabilities of FSTFPMLM are compared with other topologies of linear machines. Finally, the prototype and experimental setup have been developed, and the calculated results and the measured results are in good agreement.

Hydrogen-rich superhydrides are believed to be very promising high critical temperature (high $T_c$) superconductors, with experimentally observed critical temperatures near room temperature, as shown in recently discovered lanthanide superhydrides at very high pressures, e.g., ${\mathrm{LaH}}_{10}$ at 170 GPa and ${\mathrm{CeH}}_9$ at 150 GPa. With the motivation of discovering new hydrogen-rich high $T_c$ superconductors at the lowest possible pressure, quantitative theoretical predictions are needed. In these promising compounds, superconductivity is mediated by the highly energetic lattice vibrations associated with hydrogen and their interplay with the electronic structure, requiring fine descriptions of the electronic properties, notoriously challenging for correlated $f$ systems. In this paper, we propose a first-principles calculation platform with the inclusion of many-body corrections to evaluate the detailed physical properties of the Ce-H system and to understand the structure, stability, and superconductivity of ${\mathrm{CeH}}_9$ at high pressure. We report how the calculation of $T_c$ is affected by the hierarchy of many-body corrections and obtain a compelling increase in $T_c$ at the highest level of theory, which goes in the direction of experimental observations. Our findings shed significant light on the search for superhydrides in close similarity with atomic hydrogen within a feasible pressure range. We provide a practical platform to further investigate and understand conventional superconductivity in hydrogen-rich superhydrides.

Hydrogen-rich superhydrides are promising high-$T_c$ superconductors, with superconductivity experimentally observed near room temperature, as shown in recently discovered lanthanide superhydrides at very high pressures, e.g., LaH${}_{10}$ at 170 GPa and CeH${}_9$ at 150 GPa. Superconductivity is believed to be closely related to the high vibrational modes of the bound hydrogen ions. Here, we studied the limit of extreme pressures (above 200 GPa) where lanthanide hydrides with large hydrogen content have been reported. We focused on LaH${}_{16}$ and CeH${}_{16}$, two prototype candidates for achieving a large electronic contribution from hydrogen in the electron–phonon coupling. In this work, we propose a first-principles calculation platform with the inclusion of many-body corrections to evaluate the detailed physical properties of the Ce–H and La–H systems and to understand the structure, stability, and superconductivity of these systems at ultra-high pressure. We provide a practical approach to further investigate conventional superconductivity in hydrogen-rich superhydrides. We report that density functional theory provides accurate structure and phonon frequencies, but many-body corrections lead to an increase of the critical temperature, which is associated with the spectral weight transfer of the f-states.

Molybdenum clusters, characterized by their unique structure and intriguing catalytic properties, have gained significant attention in recent years. In several existing studies, density functional theory (DFT) methods have been used to find the lowest energy Mo clusters and explore their electronic and magnetic structure. In all cases, with the exception of a single recent study, where a genetic algorithm was employed, initial geometries of the clusters, prior to geometry optimization, were chosen using heuristic approaches based on symmetry considerations and known structures. DFT calculations were performed using different types of pseudopotentials, from soft to hard, and different types of basis sets. However, no comprehensive study has yet been carried out in which a DFT method with the best control on its precision would be complemented by a reliable global minimum search method to find the lowest energy Mo clusters. In this work, we employ a combination of a plane wave-based DFT method and ab initio random structure searching technique to find the lowest energy clusters of up to 10 Mo atoms. In each case, the search has been performed for clusters with different spin multiplicities, which enabled us to explore their magnetic structure. The results are compared for both hard and soft pseudopotentials stressing the importance of treating more electrons explicitly, in agreement with some of the previous studies. For most of the low-energy magnetic structures found, we investigate the distribution of their spin densities, and for all low energy clusters, we confirm their stability by calculating their vibrational structure. For a few smallest clusters, the results of multiconfigurational quantum chemistry calculations are also discussed. Finally, free energies of the Mo clusters, within the quasi-harmonic approximation, are also calculated and discussed.

Lanthanide hydrogen-rich materials have long been considered as one of the candidates with high-temperature superconducting properties in condensed matter physics, and have been a popular topic of research. Attempts to investigate the effects of different compositions of lanthanide hydrogen-rich materials are ongoing, with predictions and experimental studies in recent years showing that substances such as LaH${}_{10}$, CeH${}_9$, and LaH${}_{16}$ exhibit extremely high superconducting temperatures between 150–250 GPa. In particular, researchers have noted that, in those materials, a rise in the f orbit character at the Fermi level combined with the presence of hydrogen vibration modes at the same low energy scale will lead to an increase in the superconducting transition temperature. Here, we further elaborate on the effect of the ratios of lanthanide to hydrogen in these substances with the aim of bringing more clarity to the study of superhydrides in these extreme cases by comparing a variety of lanthanide hydrogen-rich materials with different ratios using the dynamical mean-field theory (DMFT) method, and provide ideas for later structural predictions and material property studies.