In the quest for finding novel thermodynamically stable, layered, MAB phases promising for synthesis, we herein explore the phase stability of ternary MAB phases by considering both orthorhombic and hexagonal...
A desired prerequisite when performing a quantum mechanical calculation is to have an initial idea of the atomic positions within an approximate crystal structure. The atomic positions combined should result in a system located in, or close to, an energy minimum. However, designing low-energy structures may be a challenging task when prior knowledge is scarce, specifically for large multi-component systems where the degrees of freedom are close to infinite. In this paper, we propose a method for identification of low-energy crystal structures within multi-component systems by combining cluster expansion and crystal structure predictions with density-functional theory calculations. Crystal structure prediction searches are applied to the Mo2AlB2 and Sc2AlB2 ternary systems to identify candidate structures, which are subsequently used to explore the quaternary (pseudo-binary) (MoxSc1–x)2AlB2 system through the cluster expansion formalism utilizing the ground-state search approach. Furthermore, we show that utilizing low-energy structures found within the cluster expansion ground-state search as seed structures within crystal structure predictions of (MoxSc1–x)2AlB2 can significantly reduce the computational demands. With this combined approach, we not only correctly identified the recently discovered Mo4/3Sc2/3AlB2i-MAB phase, comprised of in-plane chemical ordering of Mo and Sc and with Al in a Kagomé lattice, but also predict additional low-energy structures at various concentrations. This result demonstrates that combining crystal structure prediction with cluster expansion provides a path for identifying low-energy crystal structures in multi-component systems by employing the strengths from both frameworks.
common and well-known phenomenon that people tend to underestimate their sensitivity to UV radiation (13-15), with the possible outcome of not protecting themselves sufficiently. Although widely accepted, several studies have reported that there is a poor correlation between Fitzpatrick's classification and actual UV-sensitivity assessed by objective measures, such as by phototesting (14-18). If possible to create a risk score to a lesser degree dependent on subjective measurements, it would probably benefit the prerequisites to succeed with preventive efforts, or at least, to direct these efforts to the individuals in most adequate need of them.The aim of this study was to investigate whether the addition of objective variables, by means of UV-sensitivity phototesting and nevi count, could be of contributory value for the composition of a comprehensive risk score for skin cancer. The study also sought to investigate whether the use of such a score could contribute to change of behavior in the sun after assessment of individual risk.
The recent discovery of chemical ordering in quaternary
borides
offers new ways of exploring properties and functionalities of these
laminated phases. Here, we have synthesized and investigated chemical
ordering of the laminated Mo4MnSiB2 (T2) phase,
thereby introducing a magnetic element into the family of materials
coined o-MAB phases. By X-ray diffraction and scanning transmission
electron microscopy, we provide evidence for out-of-plane chemical
ordering of Mo and Mn, with Mo occupying the 16l site and Mn preferentially
residing in the 4c site. Mn and B constitute quasi-two-dimensional
layers in the laminated material. We have therefore also studied the
magnetic properties by magnetometry, and no sign of long-range magnetic
order is observed. An initial assessment of the magnetic ordering
has been further studied by density functional theory (DFT) calculations,
and while we find an antiferromagnetic configuration to be the most
stable one, ferromagnetic ordering is very close in energy.
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