adds n integrand function

pysuperconductor/os_gap_calc.py

@@ -33,3 +33,10 @@ def find_gap(temp, mu_star, debye_frequency, nv):
 		x0=debye_frequency / (numpy.sinh(nv_inv))
 	)
 	return sol.x
+
+
+def n_integrand_function(xi, temp, delta, mu_star):
+	big_e = energy(xi, delta)
+	left = 1 / (1 + numpy.exp((big_e - mu_star) / temp))
+	right = 1 / (1 + numpy.exp(big_e / temp))
+	return left - right

tests/test_os_gap_calc.py

@@ -46,3 +46,12 @@ def test_gap():
 		decimal=7, err_msg='had trouble with gap at non-zero temp and mustar',
 		verbose=True
 	)
+
+
+def test_n_integrand_function():
+	actual = pysuperconductor.os_gap_calc.n_integrand_function(1, 2, 2, 1)
+	numpy.testing.assert_almost_equal(
+		actual, 0.1038525814172795,
+		decimal=7, err_msg='did not find correct n integrand value',
+		verbose=True
+	)