(x-xn)<(E△=2Em)yEA bonding energy between A-A atoms EEE BB bonding energy between B-B atoms AB bonding energy between A-B atomsEAA—— bonding energy between A-A atoms EBB—— bonding energy between B-B atoms EAB—— bonding energy between A-B atoms ( ) AB 2 AA BB A B ) 2 ( E E E X X − − − 