Compact, orthogonal, and complete basis sets for solving the Schrodinger   equation
  We present a new type of basis set which is local, compact, and orthogonal. The basis functions, called orthlets, are centered at the sites of a lattice and are specifically adapted to represent the system being studied. The adaptability includes the ability to have singular behavior within an orthlet, allowing a single orthlet to represent a function in the vicinity of a singularity. 
Steven R. White