For simple point groups , the values are either 1 or − 1 : 1 means that the sign or phase ( of the vector or orbital ) is unchanged by the symmetry operation ( `` symmetric '' ) and − 1 denotes a sign change ( `` asymmetric '' ) .
For simple point groups , the values are either 1 or -1 : 1 means that the sign or phase ( of the vector or orbital ) is unchanged by the symmetry operation ( `` symmetric '' ) and -1 denotes a sign change ( `` asymmetric '' ) .