Symmetry and dimensionality are essential factors defining lattice dynamics and conductivity (κ). Here, we critically examine these via ab initio Boltzmann transport applied to single chain and bulk electride $\mathrm{B}{\mathrm{a}}_3\mathrm{N}$ and $\mathrm{B}{\mathrm{a}}_3\mathrm{N}X$ ($X=\mathrm{Sb}$,Bi). Chiral phonons in one-dimensional chains obey new symmetry-based scattering rules that limit thermal resistance. Weak chain coupling breaks these in the bulk, giving lower κ and large κ anisotropy. Curiously, intercalation of large X atoms binds chains more strongly, reducing the volume, yet gives lower κ and transforms the electronic behavior. Insights developed here can be more generally applied to other materials and provide avenues for predictive materials design.

• Received 5 October 2018

DOI:https://doi.org/10.1103/PhysRevB.98.241405