diff --git a/gprMax/materials.py b/gprMax/materials.py
index 37562f97..b14aaa52 100644
--- a/gprMax/materials.py
+++ b/gprMax/materials.py
@@ -106,13 +106,13 @@ class Material(object):
                 elif self.type == 'lorentz':
                     # tau for Lorentz materials are pole frequencies
                     # alpha for Lorentz materials are the damping coefficients
-                    wp2 = (2 * np.pi * self.tau[x]) * (2 * np.pi * (1 / self.tau[x]))
-                    self.w[x] = -(wp2 * self.deltaer[x]) * 1j / np.sqrt(wp2 - (self.alpha[x] * self.alpha[x]))
-                    self.q[x] = -self.alpha[x] + np.sqrt(wp2 - (self.alpha[x] * self.alpha[x])) * 1j
+                    wp2 = (2 * np.pi * self.tau[x])**2
+                    self.w[x] = -1j * ((wp2 * self.deltaer[x]) / np.sqrt(wp2 - self.alpha[x]**2))
+                    self.q[x] = -self.alpha[x] + (1j * np.sqrt(wp2 - self.alpha[x]**2))
                 elif self.type == 'drude':
                     # tau for Drude materials are pole frequencies
                     # alpha for Drude materials are the inverse of relaxation times
-                    wp2 = (2 * np.pi * self.tau[x]) * (2 * np.pi * self.tau[x])
+                    wp2 = (2 * np.pi * self.tau[x])**2
                     self.se += wp2 / self.alpha[x]
                     self.w[x] = - (wp2 / self.alpha[x])
                     self.q[x] = - self.alpha[x]