Prediction and Synthesis of Strain Tolerant RbCuTe Crystals Based on Rotation of One-Dimensional Nano Ribbons within a Three-Dimensional Inorganic Network

A unique
possibility for a simple strain tolerant inorganic solid
is envisioned whereby a set of isolated, one-dimensional (1D) nano
objects are embedded in an elastically soft three-dimensional (3D)
atomic matrix thus forming an interdimensional hybrid structure (IDHS).
We predict theoretically that the concerted rotation of 1D nano objects
could allow such IDHSs to tolerate large strain values with impunity.
Searching theoretically among the 1:1:1 ABX compounds of I-I-VI composition,
we identified, via first-principles thermodynamic theory, RbCuTe,
which is a previously unreported but now predicted-to-be-stable compound
in the MgSrSi-type structure, in space group Pnma. The predicted structure of RbCuTe consists of ribbons of copper
and telluride atoms placed antipolar to one another throughout the
lattice with rubidium atoms acting as a matrix. A novel synthetic
adaptation utilizing liquid rubidium and vacuum annealing of the mixed
elemental reagents in fused silica tubes as well as in situ (performed at the Advanced Photon Source) and ex situ structure determination confirmed the stability and predicted structure
of RbCuTe. First-principles calculations then showed that the application
of up to ∼30% uniaxial strain on the ground-state structure
result in a buildup of internal stress not exceeding 0.5 GPa. The
increase in total energy is 15-fold smaller than what is obtained
for the same RbCuTe material but in structures having a contiguous
set of 3D chemical bonds spanning the entire crystal. Furthermore,
electronic structure calculations revealed that the HOMO is a 1D energy
band localized on the CuTe ribbons and that the 1D insulating band
structure is also resilient to such large strains. This combined theory
and experiment study reveals a new type of strain tolerant inorganic
material.