simplifying LEQI docstring math and removing unnecessary operations (#2705)

openmc/deplete/_matrix_funcs.py

@@ -77,4 +77,4 @@ def leqi_f4(chain, inputs, fission_yields=None):
     return (-dt ** 2 / (12 * dt_l * (dt + dt_l)) * f1
             + (dt ** 2 + 2 * dt * dt_l + dt_l ** 2)
             / (12 * dt_l * (dt + dt_l)) * f2
-            + (4 * dt * dt_l + 5 * dt_l ** 2) / (12 * dt_l * (dt + dt_l)) * f3)
+            + (4 * dt + 5 * dt_l) / (12 * (dt + dt_l)) * f3)

openmc/deplete/integrators.py

@@ -360,8 +360,7 @@ class LEQIIntegrator(Integrator):
               h_i)} \mathbf{A}_0 + \frac{h_{i-1}}{12 (h_{i-1} + h_i)} \mathbf{A}_1 \\
         \mathbf{F}_4 &= \frac{-h_i^2}{12 h_{i-1} (h_{i-1} + h_i)} \mathbf{A}_{-1} +
               \frac{h_{i-1}^2 + 2 h_i h_{i-1} + h_i^2}{12 h_{i-1} (h_{i-1} + h_i)}
-              \mathbf{A}_0 + \frac{5 h_{i-1}^2 + 4 h_i h_{i-1}}{12 h_{i-1}
-              (h_{i-1} + h_i)} \mathbf{A}_1 \\
+              \mathbf{A}_0 + \frac{5 h_{i-1} + 4 h_i}{12 (h_{i-1} + h_i)} \mathbf{A}_1 \\
         \mathbf{n}_{i+1} &= \exp(h_i \mathbf{F}_4) \exp(h_i \mathbf{F}_3) \mathbf{n}_i
         \end{aligned}