Papers detailing the calculations of Pasquarello, Hyberston, and Car:
 
 

Spherosiloxane H8Si8O12 clusters on Si(001): First-Principles calculation of Si 2p core level shifts.  Physical Review B, 54, R2339 (1996).

Theory of Si 2p Core-Level Shifts at the Si(001)-SiO2 Interface, Physical Review B, 53, 10942 (1996)

Si 2p Core-Level Shifts at the Si(001) -SiO2 Interface: A First-Principles Study, Physical Review Letters,  74, 1024 (1995).