Solving the two dimensional Schr\"odinger equation using basis   truncation: a controversial case
  Solutions of the Schr\"odinger equation by spanning the wave function is a complete basis is a common practice is many-body interacting systems. We shall study the case of a two-dimensional quantum system composed by two interacting spin-less electrons and see that the correctness of the matrix approach depends inexplicably on the type of interaction existing between particles. 
J. Batle
quant-ph