倒易点阵(reciprocal lattice) First introduced by Peter Paul Ewald in 1921 a*.b=a*.c=b*.a=b*.c=c*.a=c*.b=0 a*·a=b*.b=c*.c=1 V。V*E1 6* 12倒易点阵(reciprocal lattice) • First introduced by Peter Paul Ewald in 1921 12 V● V*≡1