# Interstitial impurity. Carbon in iron

1. ### naggy

60
I'm trying to calculate how many carbon impurity atoms can fit into an FCC and BCC structure of Iron. It's given that the radius of carbon is 0.071nm and the radius of Iron is 0.124nm.

Can I use the Atomic packing factor? I'm sort of lost in how to approach this.

This is a pic of BCC and FCC

http://www.iap.tuwien.ac.at/www/surface/STM_Gallery/fcc_bcc.gif