pwtools.eos.EosFit

class pwtools.eos.EosFit(volume, energy, func=<pwtools.eos.Vinet object>, splpoints=500)

Bases: Fit1D

E(V) fit class.

Examples

>>> from pwtools.eos import EosFit
>>> from pwtools.constants import eV_by_Ang3_to_GPa
>>> V = linspace(30, 50, 20)
>>> E = (V-40)**2.0 / 50.0 + 30 + rand(len(V)) / 5.0
>>> plot(V, E, 'o')
>>> f = EosFit(V, E)
>>> vv = linspace(V.min(), V.max(), 200)
>>> plot(vv, f(vv), 'r-')
>>> v0 = f.params['v0']
>>> print("compare fit params and values obtained from methods:")
>>> print("V0: %f Ang^3 (%f)" %(v0, f.get_min()))
>>> print("B0: %f GPa   (%f)" %(f.params['b0']*eV_by_Ang3_to_GPa, f.bulkmod(v0)))
>>> print("B1: %f           " %f.params['b1'])
>>> print("E0: %f  eV   (%f)" %(f.params['e0'], f(v0)))
>>> print("P0: %f GPa       " %f.pressure(v0))

__init__(volume, energy, func=<pwtools.eos.Vinet object>, splpoints=500)

Parameters:

• volume (1d array) – volume per atom [Ang^3]

• energy (1d array) – total energy per atom [eV]

• func (EVFunction instance)

• splpoints (int) – number of spline points for fallback derivative calculation

__call__(volume, der=0)

Parameters:

• volume (scalar, 1d array) – volume per atom [Ang^3]

• der (int) – derivative order

Methods

bulkmod(volume)	B(V) [GPa]
fit()	Fit E(V) model, fill self.params.
get_max([x0, xab])	Convenience method.
get_min()	V0 [Ang^3]
get_root([x0, xab])	Return x where y(x) = 0 by calculating the root of the fit function.
is_mono()	Return True if the curve described by the fit function f(x) is monotonic.
pressure(volume)	P(V) [GPa]

Attributes

spl