High-order basis functions for singular currents at corners

The use of a full Motz-like expansion for the current density in the cells adjacent to the corners of a conducting scatterer provides a substantial improvement in accuracy, compared to the use of a representation that only employs the leading-order singularity. Furthermore, as the order of the expansion is increased in conjunction with that in the non-corner cells, the slope of the resulting error curve increases, confirming that higher-order behavior is obtained.