Bandgap values on NOMAD Archive

NOMAD and FAIRmat
1

Hi,
I didn’t find any bandgap values ​​on NOMAD Archive. In the dos or band structure section, we can see the DOS or band structure figure, and some vectors such as dos_energies, dos_values… Is there a way to get the bandgap values ​​from this data? thank you very much!

2

Hi @xhu!

We do extract the band gap from both the electronic structure and the density of states. In the archive band gaps extracted from BS go to results.properties.electronic.band_structure_electronic.band_gap (example) and band gaps extracted from DOS go to results.properties.electronic.dos_electronic.band_gap (example).

Although we store band gap values from both DOS and BS, our search interface currently only works on the band gaps extracted from the band structure, since they contain more information, like whether the gap is direct or indirect. This may change in the future as we would like to make band gap information from all different sources more easily searchable.

Here is an example of how you could also programmatically query for band gap values using python and our API:

import requests
import json

response = requests.post(
    'http://nomad-lab.eu/prod/v1/api/v1/entries/query',
    json={
        'query': {
            'results.properties.electronic.band_structure_electronic.band_gap.value': {
                'gt': 0,
                'lte': 8.0109e-19,  # in SI units (joule)
            }
        },
        'pagination': {
            'page_size': 10
        },
        'required': {
            'include': [
                'entry_id',
                'results.properties.electronic.band_structure_electronic.band_gap.value',
                'results.properties.electronic.band_structure_electronic.band_gap.type'
            ]
        }
    })

response_json = response.json()
print(json.dumps(response.json(), indent=2))

You can find more information about API usage in our documentation page.

Hope this helps!