/usr/share/pyshared/ase/utils/eos.py is in python-ase 3.6.0.2515-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 | # -*- coding: utf-8 -*-
from math import sqrt
import numpy as np
from ase.units import kJ
class EquationOfState:
"""Fit equation of state for bulk systems.
The following equation is used::
2 3 -1/3
E(V) = c + c t + c t + c t , t = V
0 1 2 3
Use::
eos = EquationOfState(volumes, energies)
v0, e0, B = eos.fit()
eos.plot()
"""
def __init__(self, volumes, energies):
self.v = np.array(volumes)
self.e = np.array(energies)
self.v0 = None
def fit(self):
"""Calculate volume, energy, and bulk modulus.
Returns the optimal volume, the minumum energy, and the bulk
modulus. Notice that the ASE units for the bulk modulus is
eV/Angstrom^3 - to get the value in GPa, do this::
v0, e0, B = eos.fit()
print B / kJ * 1.0e24, 'GPa'
"""
fit0 = np.poly1d(np.polyfit(self.v**-(1.0 / 3), self.e, 3))
fit1 = np.polyder(fit0, 1)
fit2 = np.polyder(fit1, 1)
self.v0 = None
for t in np.roots(fit1):
if t > 0 and fit2(t) > 0:
self.v0 = t**-3
break
if self.v0 is None:
raise ValueError('No minimum!')
self.e0 = fit0(t)
self.B = t**5 * fit2(t) / 9
self.fit0 = fit0
return self.v0, self.e0, self.B
def plot(self, filename=None, show=None):
"""Plot fitted energy curve.
Uses Matplotlib to plot the energy curve. Use *show=True* to
show the figure and *filename='abc.png'* or
*filename='abc.eps'* to save the figure to a file."""
#import matplotlib.pyplot as plt
import pylab as plt
if self.v0 is None:
self.fit()
if filename is None and show is None:
show = True
x = 3.95
f = plt.figure(figsize=(x * 2.5**0.5, x))
f.subplots_adjust(left=0.12, right=0.9, top=0.9, bottom=0.15)
plt.plot(self.v, self.e, 'o')
x = np.linspace(min(self.v), max(self.v), 100)
plt.plot(x, self.fit0(x**-(1.0 / 3)), '-r')
plt.xlabel(u'volume [Å^3]')
plt.ylabel(u'energy [eV]')
plt.title(u'E: %.3f eV, V: %.3f Å^3, B: %.3f GPa' %
(self.e0, self.v0, self.B / kJ * 1.0e24))
if show:
plt.show()
if filename is not None:
f.savefig(filename)
return f
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