https://www.google.ch/?gfe_rd=cr&ei=s2txVpjvDoXF8AfwyorQAg&gws_rd=ssl#q=gsas quantitative phase analysis
http://www.ccp14.ac.uk/solution/gsas/files/expgui_quant_gualtieri.pdf

wi = (scale factor * unit cell mass * unit cell volume)i / sum(scale factor * unit cell mass * unit cell volume)

unit cell mass = number of atom in unit cell * atomic mass/avogadro number = ? (g)

精修后的scale factor 决定了质量百分比。