Source code for burnman.processchemistry

# This file is part of BurnMan - a thermoelastic and thermodynamic toolkit for the Earth and Planetary Sciences
# Copyright (C) 2012 - 2015 by the BurnMan team, released under the GNU
# GPL v2 or later.


# This module provides the functions required to process the standard burnman formula compositions
# ProcessChemistry returns the number of atoms and molar mass of a compound given its unit formula as an argument.
# process_solution_chemistry returns information required to calculate
# solid solution properties from a set of endmember formulae

from __future__ import absolute_import
import re
import numpy as np
from fractions import Fraction
import pkgutil


[docs]def read_masses(): """ A simple function to read a file with a two column list of elements and their masses into a dictionary """ datastream = pkgutil.get_data( 'burnman', 'data/input_masses/atomic_masses.dat') datalines = [line.strip() for line in datastream.decode('ascii').split('\n') if line.strip()] lookup = dict() for line in datalines: data = "%".join(line.split("%")[:1]).split() if data != []: lookup[data[0]] = float(data[1]) return lookup
[docs]def dictionarize_formula(formula): """ A function to read a chemical formula string and convert it into a dictionary """ f = dict() elements = re.findall('[A-Z][^A-Z]*', formula) for element in elements: element_name = re.split('[0-9][^A-Z]*', element)[0] element_atoms = re.findall('[0-9][^A-Z]*', element) if len(element_atoms) == 0: element_atoms = Fraction(1.0) else: element_atoms = Fraction(element_atoms[0]) f[element_name] = f.get(element_name, 0.0) + element_atoms return f
[docs]def formula_mass(formula, atomic_masses): """ A function to take chemical formula and atomic mass dictionaries and """ mass = sum( formula[element] * atomic_masses[element] for element in formula) return mass
[docs]def dictionarize_site_formula(formula): """ A function to take a chemical formula with sites specified by square brackets and return a standard dictionary with element keys and atoms of each element per formula unit as items. """ solution_formulae = dict() s = re.split(r'\[', formula)[1:] sites = [[] for i in range(len(s))] list_occupancies = [] list_multiplicity = np.empty(shape=(len(s))) n_occupancies = 0 f = dict() for site in range(len(s)): site_occupancy = re.split(r'\]', s[site])[0] mult = re.split('[A-Z][^A-Z]*', re.split(r'\]', s[site])[1])[0] not_in_site = str(filter(None, re.split(r'\]', s[site])))[1] not_in_site = not_in_site.replace(mult, '', 1) if mult == '': list_multiplicity[site] = 1.0 else: list_multiplicity[site] = mult # Loop over elements on a site elements = re.findall('[A-Z][^A-Z]*', site_occupancy) for i in range(len(elements)): element_on_site = re.split('[0-9][^A-Z]*', elements[i])[0] proportion_element_on_site = re.findall( '[0-9][^A-Z]*', elements[i]) if len(proportion_element_on_site) == 0: proportion_element_on_site = Fraction(1.0) else: proportion_element_on_site = Fraction( proportion_element_on_site[0]) n_element = float(mult) * proportion_element_on_site f[element_on_site] = f.get(element_on_site, 0.0) + n_element # Loop over elements not on a site for enamenumber in re.findall('[A-Z][^A-Z]*', not_in_site): element = str(filter(None, re.split(r'(\d+)', enamenumber))) f[element[0]] = f.get(element[0], 0.0) + float(element[1]) return f
[docs]def process_solution_chemistry(formulae): """ This function parses a set of endmember formulae containing site information, e.g. [ '[Mg]3[Al]2Si3O12', '[Mg]3[Mg1/2Si1/2]2Si3O12' ] It outputs the bulk composition of each endmember (removing the site information), and also a set of variables and arrays which contain the site information. These are output in a format that can easily be used to calculate activities and gibbs free energies, given molar fractions of the phases and pressure and temperature where necessary. Parameters ---------- formulae : list of strings List of chemical formulae with site information Returns ------- solution_formulae : list of dictionaries List of endmember formulae is output from site formula strings n_sites : integer Number of sites in the solid solution. Should be the same for all endmembers. sites : list of lists of strings A list of elements for each site in the solid solution n_occupancies : integer Sum of the number of possible elements on each of the sites in the solid solution. Example: A binary solution [[A][B],[B][C1/2D1/2]] would have n_occupancies = 5, with two possible elements on Site 1 and three on Site 2 endmember_occupancies : 2d array of floats A 1D array for each endmember in the solid solution, containing the number of atoms of each element on each site. site_multiplicities : array of floats The number of each site per formula unit To simplify computations later, the multiplicities are repeated for each element on each site """ n_sites = formulae[0].count('[') n_endmembers = len(formulae) # Check the number of sites is the same for all endmembers for i in range(n_endmembers): assert(formulae[i].count('[') == n_sites) solution_formulae = [] sites = [[] for i in range(n_sites)] list_occupancies = [] list_multiplicity = np.empty(shape=(n_sites)) n_occupancies = 0 # Number of unique site occupancies (e.g.. Mg on X etc.) for endmember in range(n_endmembers): solution_formula = dict() list_occupancies.append([[0] * len(sites[site]) for site in range(n_sites)]) s = re.split(r'\[', formulae[endmember])[1:] for site in range(n_sites): site_split = re.split(r'\]', s[site]) site_occupancy = site_split[0] mult = re.split('[A-Z][^A-Z]*', site_split[1])[0] if mult == '': list_multiplicity[site] = 1.0 else: list_multiplicity[site] = float(mult) # Loop over elements on a site elements = re.findall('[A-Z][^A-Z]*', site_occupancy) for i in range(len(elements)): # Find the element and proportion on the site element_split = re.split('([0-9][^A-Z]*)', elements[i]) element_on_site = element_split[0] if len(element_split) == 1: proportion_element_on_site = Fraction(1.0) else: proportion_element_on_site = Fraction(element_split[1]) solution_formula[element_on_site] = solution_formula.get( element_on_site, 0.0) + list_multiplicity[site] * proportion_element_on_site if element_on_site not in sites[site]: n_occupancies += 1 sites[site].append(element_on_site) element_index = sites[site].index(element_on_site) for parsed_mbr in range(len(list_occupancies)): list_occupancies[parsed_mbr][site].append(0) else: element_index = sites[site].index(element_on_site) list_occupancies[endmember][site][ element_index] = proportion_element_on_site # Loop over elements after site if len(site_split) != 1: not_in_site = str(filter(None, site_split[1])) not_in_site = not_in_site.replace(mult, '', 1) for enamenumber in re.findall('[A-Z][^A-Z]*', not_in_site): element = list( filter(None, re.split(r'(\d+)', enamenumber))) # Look up number of atoms of element if len(element) == 1: nel = 1. else: nel = float(float(element[1])) solution_formula[element[0]] = solution_formula.get( element[0], 0.0) + nel solution_formulae.append(solution_formula) # Site occupancies and multiplicities endmember_occupancies = np.empty(shape=(n_endmembers, n_occupancies)) site_multiplicities = np.empty(shape=(n_occupancies)) for endmember in range(n_endmembers): n_element = 0 for site in range(n_sites): for element in range(len(list_occupancies[endmember][site])): endmember_occupancies[endmember][ n_element] = list_occupancies[endmember][site][element] site_multiplicities[n_element] = list_multiplicity[site] n_element += 1 return solution_formulae, n_sites, sites, n_occupancies, endmember_occupancies, site_multiplicities
[docs]def compositional_array(formulae): """ Parameters ---------- formulae : list of dictionaries List of chemical formulae Returns ------- formula_array : 2D array of floats Array of endmember formulae elements : List of strings List of elements """ elements = [] for formula in formulae: for element in formula: if element not in elements: elements.append(element) formula_array = ordered_compositional_array(formulae, elements) return formula_array, elements
[docs]def ordered_compositional_array(formulae, elements): """ Parameters ---------- formulae : list of dictionaries List of chemical formulae elements : List of strings List of elements Returns ------- formula_array : 2D array of floats Array of endmember formulae """ formula_array = np.zeros(shape=(len(formulae), len(elements))) for idx, formula in enumerate(formulae): for element in formula: assert(element in elements) formula_array[idx][elements.index(element)] = formula[element] return formula_array