1. The problem statement, all variables and given/known data General solution for eccentric spheres, smaller sphere (radius, b) completely embedded within larger sphere of radius c. The centers of both spheres lie on z-axis, distance a, apart (note: c>b+a). Problem is symmetric, so consider θ=[0,∏], r=[0,c]. The inner sphere is grounded while the outer sphere is held at a potential f2(θ). 2. Relevant equations General solution (see Morse & Feshbach, 1953)is given in coordinates of larger sphere as: V(r,θ)=Ʃ1((r/a)^s×Ʃ2(A_n×(a/b)^n×[(-1)^(n-s)n!/s!(n-s)!]- (a/r)^(s+1)×Ʃ3(A_n×(b/a)^(n+1)×[s!/n!(s-n)!])P_s(cosθ) Limits of summations Ʃ1, s=0 to s=s_max (can use s_max=50) Ʃ2, n=s to n=n_max (can use n_max=50) Ʃ3, n=0 to s=s 3. The attempt at a solution I have substituted the relevant boundary conditions into the general solution and computed the unknown coefficients A_n. For the special case when the offset,a is zero,the solution behaves well (and converges nicely to prescribed boundary conditions, BCs). However, in cases where the offset is greater than zero, the solution blows up ( and does not converge to BCs). Any ideas on what might be going wrong?