Commit JT 042418

2.503 0.01476

3.54  0.001497

4.33  0.001578

5.01  -0.001224

5.597 0.000354

#Program fitting the exchange interaction

#Model curve: Bethe-Slater function

import numpy as np, pylab, tkinter

import matplotlib.pyplot as plt

from scipy.optimize import curve_fit

from decimal import *

print("Loop begin")

#Definition of the Bethe-Slater function

def func(x,a,b,c):

    return 4*a*((x/c)**2)*(1-b*(x/c)**2)*np.exp(-(x/c)**2)

#Exchange coeff table (data to fit)

rdata, Jdata = np.loadtxt('exchange_fcc_cobalt.dat', usecols=(0,1), unpack=True)

plt.plot(rdata, Jdata, 'b-', label='data')

#Perform the fit

popt, pcov = curve_fit(func, rdata, Jdata, bounds=(0, [500.,5.,5.]))

plt.plot(rdata, func(rdata, *popt), 'r--', label='fit')

#Print the fitted params

print("Parameters: a={:.10} (in meV), b={:.10} (adim), c={:.10} (in Ang)".format(*popt))

#Ploting the result

plt.xlabel('r_ij')

pylab.xlim([0,6.5])

plt.ylabel('J_ij')

plt.legend()

plt.show()

print("Loop end")

2.4824 0.01948336

2.8665 0.01109

4.0538 -0.0002176

4.753 -0.001714

4.965 -0.001986

2.495 8.3

3.524 -3.99

4.31 0.998

4.99 -0.955

5.56 0.213

2.492 0.0028027

3.524 0.0000816

4.316 0.0003537

4.984 0.0001632

5.572 0.0000408

2.495 8.3

3.524 -3.99

4.31 0.998

4.99 -0.955

5.56 0.213