An elementary formula for computing shape derivatives of EFIE system   matrix
  We derive analytical shape derivative formulas of the system matrix representing electric field integral equation discretized with Raviart-Thomas basis functions. The arising integrals are easy to compute with similar methods as the entries of the original system matrix. The results are compared to derivatives computed with automatic differentiation technique and finite differences, and are found to be in excellent agreement. 
Juhani Kataja and Jukka I. Toivanen
math.NA