Ab Initio amorphous Nb and Ta oxide structures
Data files
Abstract
Amorphous oxide layers in thin film capacitors are linked to reduced transmon qubit T1 coherence times. Ta-based capacitors outperform Nb-based ones, suggesting amorphous Ta2O5−x is less lossy than Nb2O5−x. In the associated manuscript, we investigate the microscopic features of these amorphous oxides using ab initio molecular dynamics and density functional theory, revealing the origins of the superior performance of Ta2O5−x. We establish that oxygen deficiency is less likely to occur in amorphous Ta2O5−x than in Nb2O5−x for 0 ≤ x ≤ 0.25 and for a given oxygen deficiency x, metal Ta-Ta bond formation is enhanced. Such bonds, which are accommodated by structural flaws in the amorphous network, capture electrons better than in amorphous Nb2O5−x. These thermochemical differences quench or highly suppress magnetic moments in amorphous Ta2O5−x and eliminate a potential source of quasiparticles and magnetic flux noise. This dataset compiles the Nb2O5−x and Ta2O5−x structures generated using ab inito molecular dynamics.
Dataset DOI: 10.5061/dryad.x3ffbg7z0
Description of the data and file structure
This dataset contains the 49 Nb2O5-x and 49 Ta2O5-x structures generating using ab initio molecular dynamics and across the compositional range 0 <= x <= 0.25 as described in the associated manuscript.
Files and variables
File: Nb2O5.zip
Description: Contains the 49 Nb2O5-x structures generated using ab initio MD and relaxed with the PBE functional.
File: Ta2O5.zip
Description: Contains the 49 Ta2O5-x structures generated using ab initio MD and relaxed with the PBE functional.
File Naming Conventions
All files in follow the format: <Atom><value><Atom><value>_s<counter>_<functional>_relaxed.vasp
Atom– Indicates the elements in the compound (e.g., Nb, Ta, or O)value– Indicates the number of those atomic speciescounter– Numerical identifier for the structure (e.g., 1 – 7 replicas for each composition)functional– Indicates the density functional theory (DFT) exchange-correlation functional used to relax the atomic structure (e.g.,PBE= Perdew-Burke-Ernzerhof (1996))
Example: Ta48O118_s6_PBE_relaxed.vasp – The sixth DFT atomic structure for amorphous tantalum oxide with 48 Ta atoms and 118 oxygen atoms relaxed with the PBE functiona.
Code/software
Structure files are saved in VASP (Vienna Ab initio Simulation Package) POSCAR format and can be viewed using VESTA or various python libraries such as Atomic Simulation Environment.