pymatgen.analysis.pourbaix_diagram module

class IonEntry(ion, energy, name=None)[source]

Bases: pymatgen.analysis.phase_diagram.PDEntry

Object similar to PDEntry, but contains an Ion object instead of a Composition object.

  • comp – Ion object
  • energy – Energy for composition.
  • name – Optional parameter to name the entry. Defaults to the chemical formula.

A name for the entry. This is the string shown in the phase diagrams. By default, this is the reduced formula for the composition, but can be set to some other string for display purposes.


Creates a dict of composition, energy, and ion name

classmethod from_dict(d)[source]

Returns an IonEntry object from a dict.

class MultiEntry(entry_list, weights=None)[source]

Bases: pymatgen.analysis.pourbaix_diagram.PourbaixEntry

PourbaixEntry-like object for constructing multi-elemental Pourbaix diagrams.

Initializes a MultiEntry.

  • entry_list ([PourbaixEntry]) – List of component PourbaixEntries
  • weights ([float]) – Weights associated with each entry. Default is None
classmethod from_dict(d)[source]

Multientry name, i. e. the name of each entry joined by ‘ + ‘

class PourbaixDiagram(entries, comp_dict=None, conc_dict=None, filter_solids=False)[source]

Bases: object

Class to create a Pourbaix diagram from entries

  • [Entry] (entries) – Entries list containing both Solids and Ions
  • {str (conc_dict) – float}: Dictionary of compositions, defaults to equal parts of each elements
  • {str – float}: Dictionary of ion concentrations, defaults to 1e-6 for each element
  • filter_solids (bool) – applying this filter to a pourbaix diagram ensures all included phases are filtered by stability on the compositional phase diagram. This breaks some of the functionality of the analysis, though, so use with caution.

Return all entries used to generate the pourbaix diagram

find_stable_entry(pH, V)[source]

Finds stable entry at a pH,V condition :param pH: pH to find stable entry :type pH: float :param V: V to find stable entry :type V: float


get_decomposition_energy(entry, pH, V)[source]

Finds decomposition to most stable entry

  • entry (PourbaixEntry) – PourbaixEntry corresponding to compound to find the decomposition for
  • pH (float) – pH at which to find the decomposition
  • V (float) – voltage at which to find the decomposition

reaction corresponding to the decomposition

get_hull_energy(pH, V)[source]
static get_pourbaix_domains(pourbaix_entries, limits=None)[source]

Returns a set of pourbaix stable domains (i. e. polygons) in pH-V space from a list of pourbaix_entries

This function works by using scipy’s HalfspaceIntersection function to construct all of the 2-D polygons that form the boundaries of the planes corresponding to individual entry gibbs free energies as a function of pH and V. Hyperplanes of the form a*pH + b*V + 1 - g(0, 0) are constructed and supplied to HalfspaceIntersection, which then finds the boundaries of each pourbaix region using the intersection points.

  • pourbaix_entries ([PourbaixEntry]) – Pourbaix entries with which to construct stable pourbaix domains
  • limits ([[float]]) – limits in which to do the pourbaix analysis

[boundary_points]}. The list of boundary points are the sides of the N-1 dim polytope bounding the allowable ph-V range of each entry.

Return type:

Returns a dict of the form {entry

static process_multientry(entry_list, prod_comp, coeff_threshold=0.0001)[source]

Static method for finding a multientry based on a list of entries and a product composition. Essentially checks to see if a valid aqueous reaction exists between the entries and the product composition and returns a MultiEntry with weights according to the coefficients if so.

  • entry_list ([Entry]) – list of entries from which to create a MultiEntry
  • prod_comp (Composition) – composition constraint for setting weights of MultiEntry
  • coeff_threshold (float) – threshold of stoichiometric coefficients to filter, if weights are lower than this value, the entry is not returned

Returns the stable entries in the Pourbaix diagram.


Return unprocessed entries


Returns all unstable entries in the Pourbaix diagram

class PourbaixEntry(entry, entry_id=None, concentration=1e-06)[source]

Bases: monty.json.MSONable

An object encompassing all data relevant to a solid or ion in a pourbaix diagram. Each bulk solid/ion has an energy g of the form: e = e0 + 0.0591 log10(conc) - nO mu_H2O + (nH - 2nO) pH + phi (-nH + 2nO + q)

Note that the energies corresponding to the input entries should be formation energies with respect to hydrogen and oxygen gas in order for the pourbaix diagram formalism to work. This may be changed to be more flexible in the future.

Parameters:entry (ComputedEntry/ComputedStructureEntry/PDEntry/IonEntry) – An entry object

Returns dict which contains Pourbaix Entry data. Note that the pH, voltage, H2O factors are always calculated when constructing a PourbaixEntry object.


Returns composition


Returns the concentration contribution to the free energy, and should only be present when there are ions in the entry


returns energy

Returns (float): total energy of the pourbaix
entry (at pH, V = 0 vs. SHE)
energy_at_conditions(pH, V)[source]

Get free energy for a given pH and V

  • pH (float) – pH at which to evaluate free energy
  • V (float) – voltage at which to evaluate free energy

free energy at conditions


energy per atom of the pourbaix entry

Returns (float): energy per atom

classmethod from_dict(d)[source]



Sum of number of atoms minus the number of H and O in composition


Returns – energy normalized by number of non H or O atoms, e. g. for Zn2O6, energy / 2 or for AgTe3(OH)3, energy / 4

normalized_energy_at_conditions(pH, V)[source]

Energy at an electrochemical condition, compatible with numpy arrays for pH/V input

  • pH (float) – pH at condition
  • V (float) – applied potential at condition

energy normalized by number of non-O/H atoms at condition


Return number of atoms in current formula. Useful for normalization

class PourbaixPlotter(pourbaix_diagram)[source]

Bases: object

A plotter class for phase diagrams.

  • phasediagram – A PhaseDiagram object.
  • show_unstable – Whether unstable phases will be plotted as well as red crosses. Defaults to False.

Returns the vertices of the Pourbaix domain.

Parameters:entry – Entry for which domain vertices are desired
Returns:list of vertices
get_pourbaix_plot(limits=None, title=’‘, label_domains=True, plt=None)[source]

Plot Pourbaix diagram.

  • limits – 2D list containing limits of the Pourbaix diagram of the form [[xlo, xhi], [ylo, yhi]]
  • title (str) – Title to display on plot
  • label_domains (bool) – whether to label pourbaix domains
  • plt (pyplot) – Pyplot instance for plotting

plt (pyplot) - matplotlib plot object with pourbaix diagram

plot_entry_stability(entry, pH_range=None, pH_resolution=100, V_range=None, V_resolution=100, e_hull_max=1, cmap=’RdYlBu_r’, **kwargs)[source]
show(*args, **kwargs)[source]

Shows the pourbaix plot

  • *args – args to get_pourbaix_plot
  • **kwargs – kwargs to get_pourbaix_plot



Generates a label for the pourbaix plotter

Parameters:entry (PourbaixEntry or MultiEntry) – entry to get a label for

Returns either an ion object or composition object given a formula.

Parameters:formula – String formula. Eg. of ion: NaOH(aq), Na[+]; Eg. of solid: Fe2O3(s), Fe(s), Na2O
Returns:Composition/Ion object