Novel V-based MBenes are predicted and screened using a global search for precursors and surface functionalization, leading to the identification of V 4 B 6 S 2 as an anode for lithium-ion batteries (LIBs).
Doping at particular sites is a common method for increasing the thermoelectric efficiency of materials, by tuning carrier concentration and electronic structure. A secondary effect of doping, as well as defects, is to induce a volume change, usually referred to as chemical pressure, that may affect the thermoelectric efficiency. Theoretical investigations usually ignore the role of volume change in thermoelectric improvement, mostly for computational limitations. In this work, we address the role of chemical pressure on the thermoelectric properties of TaFeSb, $M\text{OsSb}$ ($M=\text{Ta,}\phantom{\rule{4.pt}{0ex}}\text{Nb}$), and $N\text{RuAs}$ ($N=\text{Ta,}\phantom{\rule{4.pt}{0ex}}\text{Nb,}\phantom{\rule{4.pt}{0ex}}\text{V}$) by using ab initio electronic structure calculations. We calculate the effect of both negative and positive pressure on the electronic structure, the Seebeck coefficient, electrical and thermal conductivity, as well as the power factor and thermoelectric performance. We argue that volume change, occurring because of defects or doping, should be regarded as an essential parameter to determine the thermoelectric efficiency accurately, as exemplified by TaFeSb. Among the investigated compounds, TaRuAs stands out for the peculiar behavior of electronic and thermoelectric properties with respect to volume change. NbOsSb also stands out, as the sole compounds whose thermoelectric efficiency is maximal in the ground state and cannot be increased via a moderate volume change. Overall, we predict that TaRuAs can be an excellent candidate for thermoelectric applications, due to its large thermoelectric efficiency at zero pressure and the possibility of increasing it by a small volume change. Direct calculations of $\mathrm{Ta}\mathrm{Ru}{\mathrm{As}}_{0.875}{\mathrm{Bi}}_{0.125}$ demonstrate the improved thermoelectric properties while also providing an estimate of the accuracy of our chemical-pressure-based modeling of the doping process.
MgH2 as one of potential solid-state hydrogen storage materials has been widely investigated during past decades due to its large capacity and abundant elemental reserves. Nonetheless, the presented ultra-high thermal stability and sluggish kinetics hinder a further application. In the present work, the Ni and Pt nano-clusters evolved from Ni@Pt core-shell nanoparticals facilitated the de/re-hydrogenation process of MgH 2 . The onset dehydrogenation temperature of MgH2+10wt.%Ni@Pt was greatly lowered by maximum 108K compared with 601K of the pristine MgH 2 , and the dehydrogenation process can be terminated below 573K. The thermal stability of the MgH2-based systerm was remarkably tailored to 69.4 kJ (mol H2)-1 from 76.2 kJ (mol H2)-1 of the pristine MgH2.Meanwhile, the hydrogen storage kinetics of MgH 2 -10 wt.% Ni@Pt was greatly improved compared with the pristine MgH 2 . Density functional theory calculations confirmed that Pt nano-clusters serving as a destabilizer and catalyst not only greatly destabilize the thermal stability of MgH 2 but also catalyze its reactions, in particular with the Pt(220) slab. The effective catalyst-reactant interfaces coupling with regulated surface determined desorption/absorption were deeply investigated and built, leading to an excellent agreement with experiments. The involving of transition metal clusters lays foundation of a new way of improving the hydrogen storage properties and paves a way of developing next-generation hydrogen storage materials.
To address the challenges of high error rates and poor generalization in current deep learning models for predicting lattice thermal conductivity (LTC), we introduce CrysGraphFormer, an innovative equivariant crystal graph...
A small amount of ${\mathrm{Nb}}_{2}{\mathrm{O}}_{5}$ catalyst is known to substantially improve the desorption thermodynamics and kinetics of $\mathrm{Mg}{\mathrm{H}}_{2}$. Using density functional theory in combination with ab initio molecular dynamics simulation, we provide theoretical understanding of the mechanism of dehydrogenation in Nb doped $\mathrm{Mg}{\mathrm{H}}_{2}$. We show that the substitution of Nb at the Mg site followed by the clustering of H around Nb is a likely pathway for hydrogen desorption. We also find that dehydrogenation from the vicinity of Mg vacancies is exothermic. However, the vacancies are not likely to play a significant role in hydrogen desorption due to their high formation energy $(3.87\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$.
Abstract Two‐dimensional MXenes, exfoliated from their parental precursors‐MAX phases, exhibit several outstanding properties and have achieved several accomplishments in a vast range of fields. Developing novel and high‐performance MXenes has become a vital task in materials science, so estimating the possibilities for exfoliation is a topic positioned at the research frontier. Here, the likelihood of exfoliating 36 M 2 AC MAX phases was explored by using density functional theory. For MAX phases, the composition‐dependent mechanical performances were investigated, highlighting evident trends, and, more essentially, improving MAX phases toughness, which can be achieved via modulating the A site. Two novel criteria were then introduced to assess the probability of exfoliating MXenes from MAX phases, having less complexity and lower computational cost than the prior studies. The excellent agreement provided by the new criteria with the reported results demonstrates that they are feasible, reliable as well as easily accessible. Furthermore, some key features that were previously suggested to be related to exfoliation are instead determined to be weakly correlated with it. We thus performed a detailed numerical analysis to locate representative and correlated features that are fundamental for the exfoliation. Our findings provide deep insight into the synthesis process and accelerate the discovery of new MXenes.
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