PHONYD: Generate Idealized Intensity Data

Author: Jim Stewart, Department of Chemistry, University of Maryland, College Park, MD 20742, USA

PHONYD generates a set of ideal "observed" structure factor amplitudes from calculated structure factor amplitudes, for purposes of testing programs. Optionally, the idealized data may be generated with random errors.

The reflection data in the input archive data bdf is read. Three quantities must be available: h,k,l, Frel (IDnum n304) and Fcal (IDnum n800). Frel will be replaced on the output bdf and if the input bdf contains I, σI and σF, these items will also be replaced. If I and σI are to be replaced, each reflection record must contain 1/Lp. In addition the absorption factor will be applied if it is in the file. For each reflection, a random number is generated from a Gaussian population with a mean of 0. and a standard deviation of 1.0. This random number is multiplied by a specified error to modify the 'perfect' F(cal) values.

Frel = Fcal * (1. + ERROR * RANNUM) / SCALE

I rel = Lp / ABSORP

File Assignments

Reads reflection data from the input archive bdf

Writes idealized reflection data to the output archive bdf

Example

PHONYD sca .53 lst 1000 err 0.01

Frel and Irel values are replaced by values derived from Fcal. The new values will have an R value of 0.01 and will have an F(rel) scale factor of .53.