Calculating Small-Angle X-Ray Scattering Intensities from Monte Carlo Results: Exploring Different Approaches on the Example of Primary Alcohols†

Matija Tomšič,^a,* Gerhard Fritz-Popovski,^b Lukáš Vlček,^c Andrej Jamnik^a
aUniversity of Ljubljana, Faculty of Chemistry and Chemical Technology, Aškerčeva 5, SI-1000 Ljubljana, Slovenia.
^bUniversity of Graz, Institute of Chemistry, Heinrichstr. 28, A-8010 Graz, Austria.
^cAcademy of Sciences of the Czech Republic, Institute of Chemical Process Fundamentals, Rozvojova 135,
 CZ-165 02 Prague 6 – Suchdol, Czech Republic.
E-mail: matija.tomsic@fkkt.uni-lj.si

Abstract
Two different approaches for the calculation of small-angle X-ray scattering (SAXS) intensities were compared and discussed on an example of Monte Carlo (MC) simulation results for primary liquid alcohols from ethanol to 1-hexanol. Recently we reported a thorough structural study on the structure of pure primary liquid alcohols from ethanol to 1- hexanol (J. Phys. Chem. B 2007, 111, 1738–1751) where also a novel approach to SAXS intensity calculations based on the well known Debye equation was introduced. The most pretentious task of this “brute force” procedure was to eliminate the background scattering of the Monte Carlo box. The method enables a direct comparison of MC data to the experimental results without prior separation of form and structure factor and offers to perform a theoretical analog to a well-known contrast matching experiment in small-angle neutron scattering. In this contribution we compare the performance of this procedure and the procedure based on the reciprocal lattice approach described by Frenkel et al. (J. Chem. Phys. 1986, 84, 4625–4630).

Keywords: SAXS, Monte Carlo simulation, alcohol, reciprocal lattice, contrast matching.