Nanostructuring is a well-established approach to improve the thermoelectric behavior of materials. However, its effectiveness is restricted if excessively small particle sizes are necessary to considerably decrease the lattice thermal...
Oxychalcogenides represent a large chemical space with potential application as thermoelectric materials due to their low thermal conductivity. However, the nature of this behaviour is still under debate. Understanding the...
Ultrahigh-temperature
ceramics (UHTCs) are a group of materials
with high technological interest because of their applications in
extreme environments. However, their characterization at high temperatures
represents the main obstacle for their fast development. Obstacles
are found from an experimental point of view, where only few laboratories
around the world have the resources to test these materials under
extreme conditions, and also from a theoretical point of view, where
actual methods are expensive and difficult to apply to large sets
of materials. Here, a new theoretical high-throughput framework for
the prediction of the thermoelastic properties of materials is introduced.
This approach can be systematically applied to any kind of crystalline
material, drastically reducing the computational cost of previous
methodologies up to 80% approximately. This new approach combines
Taylor expansion and density functional theory calculations to predict
the vibrational free energy of any arbitrary strained configuration,
which represents the bottleneck in other methods. Using this framework,
elastic constants for UHTCs have been calculated in a wide range of
temperatures with excellent agreement with experimental values, when
available. Using the elastic constants as the starting point, other
mechanical properties such a bulk modulus, shear modulus, or Poisson
ratio have been also explored, including upper and lower limits for
polycrystalline materials. Finally, this work goes beyond the isotropic
mechanical properties and represents one of the most comprehensive
and exhaustive studies of some of the most important UHTCs, charting
their anisotropy and thermal and thermodynamical properties.
Ultra-high temperature ceramics, UHTCs, are a group of materials with high technological interest because their use in extreme environments. However, their characterization at high temperatures represents the main obstacle for their fast development. Obstacles are found from a experimental point of view, where only few laboratories around the world have the resources to test these materials under extreme conditions, and also from a theoretical point of view, where actual methods are extremely expensive. Here, a new theoretical high-throughput framework for the prediction of the thermoelastic properties of materials is introduced. This approach can be systematically applied to any kind of crystalline material, drastically reducing the computational cost of previous methodologies. Elastic constants for UHTCs have been calculated at a wide range of temperatures with excellent agreement with experimentally reported values. Moreover, other mechanical properties such a bulk modulus, shear modulus or Poisson ration have been also explored. Other frameworks with similar computational cost have been used only for predicting isotropic or averaged properties, however this new approach opens the door to the calculation of anisotropic properties at a very low computational cost.
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