We provide simple polynomial fits to the X-ray photoelectric cross-sections ( 0.03 < E < 10 keV ) for mixtures of gas and dust found in protoplanetary disks .
Using the solar elemental abundances of Asplund et al .
( 2009 ) we treat the gas and dust components separately , facilitating the further exploration evolutionary processes such as grain settling and gain growth .
We find that blanketing due to advanced grain-growth ( a _ { max } > 1 \mu m ) can reduce the X-ray opacity of dust appreciably at E _ { X } \sim 1 keV , coincident with the peak of typical T Tauri X-ray spectra .
However , the reduction of dust opacity by dust settling , which is known to occur in protoplanetary disks , is probably a more significant effect .
The absorption of 1-10keV X-rays is dominated by gas opacity once the dust abundance has been reduced to about 1 % of its diffuse interstellar value .
The gas disk establishes a floor to the opacity at which point X-ray transport becomes insensitive to further dust evolution .
Our choice of fitting function follows that of Morrison & McCammon ( 1983 ) , providing a degree of backward-compatibility .