For hexagonal: cos 9 l4l2+y1V2+1w2()2-(4V2+a21) a C 1+V1-+W uiV L2)+12+1 aFor hexagonal: 2 2 2 2 2 2 2 2 1 1 2 2 2 1 2 1 2 1 1 2 2 1 2 1 2 1 2 1 2 ( ) ( ) ( ) 2 1 ( ) u v a c u v u v w a c u v w u v u v a c u u v v w w + + − + + − + + − +  cos =