250 c.N.=4 c.N.=6 cN.=8 =B4 =0.323 KtRb+ Cs+ 200 Csal O*CsF 一RbF口 150 KF 100 Nacl structure ◆ Cscl structure o Nacl Cscl structures w I-r+ plotted 50 100 150 200 r+(pm)