Improved analysis of surface X-ray data

Abstract

Abstract A new method is developed for interpreting the difference Patterson function in surface X-ray structure analysis. The difference Patterson function has negative parts which arise from subtracting the integral Patterson function from the true Patterson function. This suggests, that by adding a judiciously chosen function one may utilize the information contained in the positivity constraint for the true Patterson function. We formulate conditions on this function and find a method to construct this function. It is shown that in many cases this function coincides with the integral Patterson function of the so-called “complementary structure”. The proposed new Patterson function obtained by adding the so constructed function to the difference Patterson function is easier to interpret than the conventional difference Patterson function.