# Export phase energies as a table

This snippet can be used to export the results of a calculation to a Pandas DataFrame object.

from pycalphad import Workspace, variables as v
from pycalphad.property_framework.metaproperties import IsolatedPhase
import pandas as pd

wks = Workspace('alzn_mey.tdb', ['AL', 'ZN'],
                ['FCC_A1', 'HCP_A3', 'LIQUID'],
                {v.X('ZN'):(0,1,0.02), v.T: (300, 1000, 10), v.P:101325, v.N: 1})

props = [v.T, v.X('AL'), v.X('ZN')]
for phase_name in wks.phases:
    prop = IsolatedPhase(phase_name, wks)(f'GM({phase_name})')
    prop.display_name = f'GM({phase_name})'
    props.append(prop)

data = {f'{key.display_name} [{key.display_units}]': value.reshape(-1)
        for key, value in wks.get_dict(*props).items()}

pd.DataFrame(data)

	Temperature [kelvin]	X_AL [fraction]	X_ZN [fraction]	GM(FCC_A1) [J / mol]	GM(HCP_A3) [J / mol]	GM(LIQUID) [J / mol]
0	300.0	1.00	1.000000e-10	-8496.605675	-3555.605675	-1043.275310
1	300.0	0.98	2.000000e-02	-8564.717990	-3674.761325	-1250.180921
2	300.0	0.96	4.000000e-02	-8573.037243	-3733.289523	-1394.468476
3	300.0	0.94	6.000000e-02	-8564.854312	-3774.752790	-1519.171542
4	300.0	0.92	8.000000e-02	-8549.523829	-3808.760080	-1633.419774
...	...	...	...	...	...	...
3495	990.0	0.10	9.000000e-01	-54233.504407	-54769.630291	-58354.955825
3496	990.0	0.08	9.200000e-01	-54199.685094	-54895.795230	-58409.376195
3497	990.0	0.06	9.400000e-01	-54123.191596	-54986.670187	-58424.306318
3498	990.0	0.04	9.600000e-01	-53989.616338	-55028.419738	-58385.478971
3499	990.0	0.02	9.800000e-01	-53768.693811	-54991.395316	-58262.766288

3500 rows × 6 columns

Plot energy curves for several phases

from pycalphad import Workspace, variables as v
from pycalphad.property_framework.metaproperties import IsolatedPhase
import matplotlib.pyplot as plt

wks2 = Workspace('alzn_mey.tdb', ['AL', 'ZN'],
                ['FCC_A1', 'HCP_A3', 'LIQUID'],
                {v.X('ZN'):(0,1,0.02), v.T: 600, v.P:101325, v.N: 1})

fig = plt.figure()
ax = fig.add_subplot()

x = wks2.get(v.X('ZN'))
ax.set_xlabel(f"{v.X('ZN').display_name} [{v.X('ZN').display_units}]")

for phase_name in wks2.phases:
    # Workaround for poor starting point selection in IsolatedPhase
    metastable_wks = wks2.copy()
    metastable_wks.phases = [phase_name]
    prop = IsolatedPhase(phase_name, metastable_wks)(f'GM({phase_name})')
    prop.display_name = f'GM({phase_name})'
    ax.plot(x, wks2.get(prop), label=prop.display_name)
ax.legend()

<matplotlib.legend.Legend at 0x7f0d36725d80>

Driving force calculation

from pycalphad import Workspace, variables as v
from pycalphad.property_framework.metaproperties import DormantPhase

wks3 = Workspace('alzn_mey.tdb', ['AL', 'ZN'],
                ['FCC_A1', 'HCP_A3', 'LIQUID'],
                {v.X('ZN'):(0,1,0.02), v.T: 600, v.P:101325, v.N: 1})
metastable_liq_wks = wks3.copy()
metastable_liq_wks.phases = ['LIQUID']
liq_driving_force = DormantPhase('LIQUID', metastable_liq_wks).driving_force
liq_driving_force.display_name = 'Liquid Driving Force'

fig = plt.figure()
ax = fig.add_subplot()
ax.plot(wks3.get(v.X('ZN')), wks3.get(liq_driving_force))
ax.set_xlabel(f"{v.X('ZN').display_name} [{v.X('ZN').display_units}]")
ax.set_ylabel(f"{liq_driving_force.display_name} [{liq_driving_force.display_units}]")

Text(0, 0.5, 'Liquid Driving Force [J / mol]')

Calculate T0 (t-zero) as a function of composition

The T0 (t-zero) temperature is a thermodynamic condition in which two specified phases have the same value of the Gibbs energy. Below T0, a so-called “massive” phase transition is thermodynamically favored to occur, without a barrier to diffusion.

from pycalphad.property_framework.tzero import T0

# For T0, conditions must be one-dimensional (step calculation)
wks4 = Workspace('alzn_mey.tdb', ['AL', 'ZN'],
                ['FCC_A1', 'HCP_A3', 'LIQUID'],
                {v.X('ZN'): (0,1,0.02), v.T: 300, v.P:101325, v.N: 1})
tzero = T0('FCC_A1', 'HCP_A3', wks4)
tzero.maximum_value = 1700 # set temperature limit

fig = plt.figure()
ax = fig.add_subplot()
ax.plot(wks4.get(v.X('ZN')), wks4.get(tzero))
ax.set_xlabel(f"{v.X('ZN').display_name} [{v.X('ZN').display_units}]")
ax.set_ylabel(f"{tzero} [{tzero.display_units}]")

Text(0, 0.5, 'T0(FCC_A1,HCP_A3) [kelvin]')