Which phase of Ta2O5 being of the largest dielectric constant

As a promising dielectric material, tantalum pentoxide (Ta2O5) exhibits multi‐phase co‐existing under common fabrication conditions, so it is highly desired to predict theoretically which phase is of the largest dielectric constant. Considering that the specific operations and parameters employed in ab initio calculations may lead to considerably different lattice structure, we set the experimental lattice constants as the criteria to select the functional and parameters in density of functional theory and calculated the dielectric tensors of crystalline δ‐, β‐, LSR‐, B‐, and Z‐Ta2O5, showing that the dielectric constant is very sensitive to the lattice constants and δ‐Ta2O5 possesses the largest dielectric constant, 375.1, which is about 10 times larger than those of the other four phases and the experimental measurement of common Ta2O5 samples with several phases co‐existed, and furthermore, the dielectric constant of δ‐ and β‐Ta2O5 could be enhanced to 1175.2 and 939.5, respectively, with the Ta atom replaced by Ti atom at a molar ratio of 7.14%, which is in qualitative agreement with the experimental observations of Ti‐doped β‐, LSR‐, and H‐Ta2O5.