Ab Initio amorphous Nb and Ta oxide structures

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 u..., , # Ab initio amorphous Nb and Ta oxide structures

Dataset DOI: [10.5061/dryad.x3ffbg7z0](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 species
* `counter` – Numerical identifier for the structure (e.g., 1 – 7 re...,