High-Throughput Computation of Thermal Conductivity of High-Temperature Solid Phases: The Case of Oxide and Fluoride Perovskites

Using finite-temperature phonon calculations and machine-learning methods, we assess the mechanical stability of about 400 semiconducting oxides and fluorides with cubic perovskite structures at 0, 300, and 1000 K. We find 92 mechanically stable compounds at high temperatures—including 36 not mentioned in the literature so far—for which we calculate the thermal conductivity. We show that the thermal conductivity is generally smaller in fluorides than in oxides, largely due to a lower ionic charge, and describe simple structural descriptors that are correlated with its magnitude. Furthermore, we show that the thermal conductivities of most cubic perovskites decrease more slowly than the usual ${\mathit{T}}^{-1}$ behavior. Within this set, we also screen for materials exhibiting negative thermal expansion. Finally, we describe a strategy to accelerate the discovery of mechanically stable compounds at high temperatures.

Popular Summary

A long-term goal of computational physics is to design materials that possess specific properties. In recent decades, ab initio calculations have made formidable progress in this field, and high-throughput studies of thousands of compounds hold the promise of considerably speeding up the discovery of new materials. However, the properties of interest are usually computed at 0 K, and devices are often used at higher temperatures (i.e., 300–1000 K). Some classes of materials, like perovskites, present a rich variety of phase transitions as a function of temperature; in that context, taking into account the effects of temperature is paramount for computing thermal conductivity in high-temperature phases. Here, we focus on the thermal conductivity of fluorides and oxides with cubic perovskite structure at high temperatures.

From a chemical space containing more than 7000 compounds found in the AFLOW database, we theoretically consider the mechanical stability of roughly 400 semiconducting oxides and fluorides at three different temperatures: 0, 300, and 1000 K. Using a combination of ab initio calculations and machine-learning techniques, we screen for semiconductors and compute their mechanical stability and thermal conductivity at high temperatures. Focusing on perovskites with the highest-symmetry cubic structure—those most likely to exist at high temperatures—we find new compounds that are potentially stable and show that fluorides generally have a lower thermal conductivity than oxides. We isolate 92 compounds that are mechanically stable at high temperatures, including 36 that have thus far not been reported in the literature. We also search for materials that exhibit negative thermal expansion (i.e., shrinkage as function of increasing temperature); we find only two candidates demonstrating negative thermal expansion around room temperature.

We expect that our study will motivate the synthesis of new materials and shed light on the potential of halide perovskites for applications requiring a low thermal conductivity.

Figure 1

Workflow of the method used to calculate the phonon spectrum and thermal conductivity including finite-temperature anharmonic effects.

Figure 2

List of cubic perovskites found to be mechanically stable at 1000 K and their corresponding computed lattice thermal conductivity (in $\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$). We also report the computed lattice thermal conductivity at 300 K (in $\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$) when we obtain stability at that temperature. We highlight in blue the compounds that are experimentally reported in the ideal cubic perovskite structure, and in red those that are reported only in nonperovskite structures (references provided in the table). When no reference is provided, no mention of the compound in this stoichiometry has been found in the experimental literature. Experimental measurements of the thermal conductivity are reported in parentheses, and in italics when the structure is not cubic.

Figure 3

A comparison between total thermal conductivities from Refs. [25, 35, 51, 52, 57, 80], high-throughput calculations of the lattice thermal conductivity at 300 and 1000 K, and model behaviors in $\kappa \propto T^{-1}$ and $\kappa \propto T^{-0.7}$.

Figure 4

Depiction of strategy for exploring the relevant combinatorial space of compounds that are mechanically stable at high temperature.

Figure 5

Column number of the element at site $A$ (top) and $B$ (bottom) of the perovskite $AB{X}_3$ in the initial list of fluoride (red) and oxide (blue) paramagnetic semiconductors and after screening for mechanical stability (violet and cyan, respectively).

Figure 6

Distribution of compounds as a function of the lattice thermal conductivity at 1000 K. The red curve corresponds to the distribution for all mechanically stable compounds. The blue curve corresponds to the distribution for oxides only. The green curve corresponds to the distribution for fluorides only.

Figure 7

Correlograms between the thermal conductivity $\kappa$, the thermal conductivity in the small grain limit ${\kappa }_{\mathrm{sg}}$, the mean phonon group velocity $v_g$, the heat capacity $c_V$, the root-mean-square Grüneisen parameter ${\gamma }_{\mathrm{rms}}$, the masses $m_A$ and $m_B$ of atoms at sites $A$ and $B$ of the perovskite $AB{X}_3$, their electronegativities $e_A$, $e_B$, their Pettifor scales ${\chi }_A$, ${\chi }_B$, their ionic radii $r_A$, $r_B$, the lattice parameter of the compound $a_{\mathrm{latt}}$, and its electronic band gap, for mechanically stable fluorides (left) and oxides (right) at 1000 K.