Today, quantum chemical calculations are becoming a powerful tool to perform virtual experiments that have the capacity to predict experimentally observed non-periodic features, such as interfaces, that are responsible for quantum properties of materials. A combination of atomistic modeling, DFT calculations and HRTEM analysis provided a new fundamental insight into the structure and stability of Sb-rich basal-plane inversion boundaries (b–IBs) in ZnO. DFT screening for the most stable IB structure had an unexpected outcome – it predicted a model that was previously not known in Sb–doped ZnO, whereas the generally accepted IB model previously reported in the literature was shown to be the second most stable. This surprising result was verified by systematic HRTEM analysis of b–IBs in Sb₂O₃-doped ZnO that resulted in the experimental confirmation of the theoretically identified structure.

Firstly, IB models were designed following stringent crystallographic rules of stacking in close–packed lattices. This was followed by DFT calculations of their stabilities and analysis of energy contributions. In the course of DFT screening it was shown, that the most stable IB configuration is different from the one that was known from the literature for Sb–doped ZnO [1]. The analysis of the energetic contributions of individual stacking segments suggested that the stability of IBs is defined by their cationic stacking, and is proportional to the number of cubic bonds [2]. By our analysis, four distinct stacking segments were identified to constitute head–to–head b–IB in ZnO. In addition, we show that the energies of stacking segments can be used to predict the stability of new, hypothetical models, without the need for additional calculations. Secondly, experimental IB structures were recorded in Sb–doped ZnO at the atomic scale and the atomic positions were identified through quantitative HRTEM analysis of IBs by iterative structure refinement, image simulations and matching. Systematic reexamination of Sb–rich IBs in Sb₂O₃–doped ZnO samples revealed that both IB structures coexist in the material, whereas the newly identified IB structure does not only exist but is the most frequent one occurring in ZnO. Four elementary stacking segments identified to constitute head–to–head b–IBs and the two most stable IB structures in Sb₂O₃-doped ZnO are illustrated in Figure 1.

We show that implemented methodology that combines atomic –scale experimental methods with structure modeling and DFT calculations has the capacity to predict structural details with confidence levels down to <1 pm [2]. So accurately determined structures have great potential for solving related physical phenomena. Our study demonstrates that quantum-chemical modeling of materials can be leveraged with experimental atomic-scale electron microscopy methods to extract picometer–scale structural details from interfaces in crystalline materials. Such refined structures are fundamental to solve open questions related to their role in the electron transport, phonon scattering, debated p-type conductivity of ZnO [3], affinity of dopants to spontaneously generate IBs [4] and underlying formation mechanisms. Excellent match between calculations and experiment demonstrated in our study opens new perspectives for prediction of such properties from first principles.