Hidden structural order in orthorhombic Ta2O5.

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• The atomic structure of orthorhombic tantalum pentoxide (Ta2O5) has been debated for decades due to complex structural disorder.
• Existing models struggle to reconcile experimental observations with theoretical predictions.

Purpose of the Study:

• To determine the correct, low-energy structural model for orthorhombic Ta2O5.
• To elucidate the origins of structural disorder and dynamic symmetry in Ta2O5.

Main Methods:

• First-principles calculations were employed to investigate atomic structures.
• A novel triangular graph-paper representation was developed for analyzing Ta2O5 structures.
• Oxidation state analysis was used in conjunction with structural modeling.

Main Results:

• A new high-symmetry, low-energy structural model for Ta2O5 was identified.
• This model features correct formal oxidation states for Ta (+5) and O (-2).
• The model explains the dynamic appearance of a triangular lattice symmetry at finite temperatures and accounts for intrinsic structural variations and oxygen vacancies.

Conclusions:

• The proposed structural model provides a unified explanation for experimental observations of Ta2O5.
• Structural disorder arises from intrinsic variations and oxygen vacancies, leading to sublattice relaxation.
• This work clarifies the complex atomic structure of Ta2O5, resolving long-standing controversies.