A REVERSE MONTE-CARLO MODELING STUDY OF AMORPHOUS HYDROGENATED CARBON

The results of a Reverse Monte Carlo (RMC) modelling of amorphous hydr ogenated carbon (a-C:H) are presented. The RMC method has been impleme nted with the introduction of maximum co-ordination number and ''tripl et'' constraints, whilst fitting both neutron and X-ray diffraction da ta. The positions of 5000 ''atoms'' in a box, with full periodicity, a re altered until the associated model structure factor, S(Q), and pair distribution function, G(r), agree with the analogous experimental da ta within the errors. Once the data has been fitted, it is possible to generate model partial pair distribution functions (i.e. those associ ated with C-C, C-H and H-H), bond angle distributions, co-ordination n umber distributions, etc. X-ray data is used to provide information on the carbon-carbon network, whilst neutrons are also sensitive to the cross-terms involving hydrogen. The fitting of both types of data simu ltaneously therefore provides sufficient information to generate a via ble ''physical'' model for the structure of these materials. The effec ts of increasing the number density inside the box have also been inve stigated.