  The basic formal and numerical aspects of different degree interpolated
moving least-squares (IMLS) methods are studied using sixteen different
combinations of coordinate system for fitting and weight functions. For the
application we use six-dimensional potential energy surface (PES) of hydrogen
peroxide, for which an analytic ("exact") potential is available in the
literature. We systematically examine the effect of parameters in the weight
function, the degree of the IMLS fit, and number of ab initio points. From
these studies we discovered that the IMLS for almost all pairs of coordinate
system show qualitatively similar behavior, however, the accuracy of the fits
is noticeably different. We also found compact and accurate representations of
potentials for presented degrees of IMLS.
