hello to all here is a problem i designed myself. i don't know whether it can be solved. Question: Consider NaCl lattice of edge length 'x' m. Let Na+ carry +1 C and each Cl- carry -1 charge. Calculate Poisson's ratio of NaCl crystal. Assume no heat loss when deformation takes place. Other questions (easy): 1) Calculate the locus of a point which moves such that the sum of reciprocals of potentials due to two charges separated 'd' distance apart is constant. I will post other questions later. I will try to come up with a soln. for the Poisson's ratio problem.