Ternary sulfides and selenides in the distorted-perovskite structure (“chalcogenide perovskites”) are predicted by theory to be semiconductors with a band gap in the visible-to-infrared and may be useful for optical, electronic, and energy conversion technologies. Here we use computational thermodynamics to predict the pressure–temperature phase diagrams for select chalcogenide perovskites. Our calculations incorporate formation energies calculated by density functional theory, and empirical estimates of heat capacities. We highlight the windows of thermodynamic equilibrium between solid chalcogenide perovskites and the vapor phase at high temperature and very low pressure. These results can guide the adsorption-limited growth of ternary chalcogenides by molecular beam epitaxy.

Accelerated Molecular Dynamics (AMD) is a class of MD-based algorithms for the long-time scale simulation of atomistic systems that are characterized by rare-event transitions. Temperature-Accelerated Dynamics (TAD), a traditional AMD approach, hastens state-to-state transitions by performing MD at an elevated temperature. Recently, Speculatively-Parallel TAD (SpecTAD) was introduced, allowing the TAD procedure to exploit parallel computing systems by concurrently executing in a dynamically generated list of speculative future states. Although speculation can be very powerful, it is not always the most efficient use of parallel resources. Here, we compare the performance of speculative parallelism with a replica-based technique, similar to the Parallel Replica Dynamics method. A hybrid SpecTAD approach is also presented, in which each speculation process is further accelerated by a local set of replicas. Overall, this work motivates the use of hybrid parallelism whenever possible, as some combination of speculation and replication is typically most efficient.

This work was aimed to use the peak separation method to directly measure the critical temperatures and phase transition fractions of austenite decomposition products based on experimental dilatometric curves in hypo-eutectoid steels. The results indicated that pearlite transformation start temperature and ferrite transformation finish temperature could be clearly obtained through peak separation processing, which were generally hidden in the overlapped peaks of the linear thermal expansion coefficient curve. Moreover, four critical temperatures of austenite decomposition were retarded to lower temperature with cooling rate increasing. The phase transition fraction for austenite decomposition was quantitated by measuring the area of the corresponding phase transformation peak. The final ferrite phase fraction after austenite decomposition decreased with cooling rate increasing. On the contrary, the final pearlite phase fraction increased with cooling rate increasing. Compared with the lever rule, the calculation result using peak area method can accurately reflect the actual phase fraction change versus the temperature during austenite decomposition.

Porous carbon derived from biomass materials with enrich, low cost, clean, and renewable merits, exhibits various physical and chemical properties. So, it is of great significance to rationally utilize biomass materials for producing porous carbon with low cost to reduce overusing fossil fuel and environmental pollution. In this report, porous carbon has been fabricated using fruits shells of the Paulownia tomentosa by a facile method of KOH-activation. The as-obtained porous carbon containing a larger number of micropores and slight mesopores possesses a high specific surface area (1914.4 m2/g) and well hierarchical porosity. As the anode for sodium ion batteries, the porous carbon sample displays superior cycling stability and rate capability, delivering a reversible specific capacity of 179 mA h/g at 50 mA/g after 100 cycles and a discharge specific capacity of 100 mA h/g at 1 A/g.

Microstructural patterns resulting from self-organization are responsible for phase transitions and property changes in many materials maintained far from the thermodynamic equilibrium. Understanding the origin and the selection of possible spatiotemporal patterns for dissipative systems, i.e., systems for which the energy is not conserved, is a major theme of research opening doors to many technological applications ranging from plasmonics to metamaterials. Almost forty years after Turing’s seminal paper on patterning, progress on modeling instabilities leading to pattern formation has been achieved. The first part of this work demonstrates that main field approaches succeeded in capturing the underlying physics responsible for the formation of radiation-induced spatiotemporal patterns experimentally observed. The second part of the text highlights the interest of the phase field method, a self-consistent mean field approach, to discuss the evolution of these patterns in a universal picture neglecting specific aspects of radiation-induced dynamics.

Heat-assisted magnetic recording (HAMR) relies on careful management of heat flow at the nanoscale. This article describes the heat-transfer aspects of such a system that must be considered above and beyond standard Fourier’s Law-based heat conduction. A background on nanoscale heat transport is provided that discusses energy carriers and the role of interfaces and microstructure in nanoscale conduction. These heat-transport concepts are applied to the key components of the HAMR system—the head (principally, the near-field transducer [NFT]) and the magnetic medium. This analysis frames the central challenge of thermal engineering for a HAMR system—getting the medium hot enough while maintaining a NFT that it is cool enough to avoid degradation over time. Of particular note are discussions on the role of the interface thermal conductance in the NFT and the importance of thermal anisotropy in the medium due to its granular microstructure.

Increasing the density of data storage is crucial to the future of inexpensive digital technology. The large majority of storage in the “Cloud” consists of magnetic hard-disk drives. The continued evolution of this USD$30 billion industry depends on the commercial introduction of heat-assisted magnetic recording (HAMR). This technology uses heat from a laser beam confined well below the diffraction limit, <50-nm wide, to write to media near 450°C with high magnetic anisotropy that would normally be unwriteable under available magnetic fields. This high anisotropy guarantees thermal stability even for grain sizes around 5-nm diameter, which are necessary for major increases in storage density. In this article and in the articles in this issue, we introduce HAMR requirements and discuss its numerous interdisciplinary materials challenges, including high-temperature/efficient plasmonic materials, low-loss optical materials, highly ordered/thermally anisotropic nanoscale magnetic grains, block copolymers for directed assembly below 10 nm, high-temperature nanometer-thick coatings/lubricants, materials/interfaces to control heat flow at nanometer length scales, and advanced spintronic materials.

Heat-assisted magnetic recording (HAMR) is the next-generation technology that is required to deliver areal densities in excess of 2 terabit/in2 for high-capacity, low-cost hard drives.The recording process relies on spatially and temporally localized heating of the media surface to lower its coercivity during the magnetic writing process. This scheme drives substantial changes to the recording head write element architecture, combining the conventional electromagnet structure with integrated optical light delivery layers, focusing optics, and plasmonic nanostructures to generate subwavelength optical spots. Power losses associated with the strong optical fields required for heating the media can cause local temperatures in excess of 400°C at the recording head surface. Coupled with high pressures, an oxidative/corrosive air-bearing environment, and a sub-3 nm head-media spacing, this introduces new challenges for the functional materials in recording heads required to balance performance and long-term reliability demands. Here, we briefly review specific challenges associated with HAMR heads, highlighting the major requirements, failure modes, and needed innovations for the near-field transducer and optical-waveguide subsystems.