O2 evolution plot in Battery Explorer

KyuJung_Jun · January 9, 2021, 12:34pm

Hi,

I have one question about the O2 evolution plot in the battery explorer module in the MP website.

(1) Is the O2 evolution plot being updated as new entries are added to the MP database? This is because if I generate this plot by querying the current MP Database, although the order of decomposition reactions mostly agree, there are some decomposition reactions that do not appear on the website compared to what I have made. So I’m wondering if the MP Website O2 evolution curves are generated with an old database.

(2) Is it correct that this plot is generated with only oxygen open to exchange with the environment?

(3) According to most of the comparisons I have made between my code and the MP O2 evolution plot, is it correct that the x-axis (mu O2) is chemical potential of O2, not O? I noticed that in my code the vertex is O, not O2 and the chemical potentials at which each of the decompositions occur are about half of what is given on MP Website.

Thank you for your help!

jshen · January 12, 2021, 6:20pm

Hi KyuJung,
Thanks for the question.
The muO2 evolution is here:

github.com

materialsproject/emmet/blob/91ec995e5f9a7e0ceac6d9c5cbff32cf60a2d8f7/emmet/materials/electrodes.py#L248


assert (working_ion_entry is not None)
grouped_entries = list(self.get_sorted_subgroups(elec_entries))
docs = []  # results
for group in grouped_entries:
    self.logger.debug(
        f"Grouped entries in all sandboxes {', '.join([en.name for en in group])}"
    )
    for en in group:
        # skip this d_muO2 stuff if you do note have oxygen
        if Element('O') in en.composition.elements:
            d_muO2 = [{
                'reaction': str(itr['reaction']),
                'chempot': itr['chempot'],
                'evolution': itr['evolution']
            } for itr in phdi.get_element_profile('O', en.composition)]
        else:
            d_muO2 = None
        en.data['muO2'] = d_muO2
        en.data['decomposition_energy'] = phdi.get_e_above_hull(en)

which effectively calls this:

github.com

materialsproject/pymatgen/blob/32cad282bc919965cd2d6014be25a5459fe5a670/pymatgen/analysis/phase_diagram.py#L914-L961


def get_element_profile(self, element, comp, comp_tol=1e-5):
    """
    Provides the element evolution data for a composition.
    For example, can be used to analyze Li conversion voltages by varying
    uLi and looking at the phases formed. Also can be used to analyze O2
    evolution by varying uO2.
    Args:
        element: An element. Must be in the phase diagram.
        comp: A Composition
        comp_tol: The tolerance to use when calculating decompositions.
            Phases with amounts less than this tolerance are excluded.
            Defaults to 1e-5.
    Returns:
        Evolution data as a list of dictionaries of the following format:
        [ {'chempot': -10.487582010000001, 'evolution': -2.0,
        'reaction': Reaction Object], ...]
    """
    element = get_el_sp(element)

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My reading of the get_element_profile function is that it gets the chemical potential of O.
It would actually be really helpful to have a chat because I’m in the process of redesigning this stuff so it will be really helpful to know how people plan on using it.

Do you want to have a quick zoom chat? We can arrange it via email.