It is often observed that the CTRs of layered minerals exhibit ‘pseudo-nodes’, most often immediately adjacent to substrate Bragg peaks, and that their location (i.e., just above or below the Bragg peak) is an indication of the terminating plane of the lattice (i.e., A- or B-termination, above). This has been used as a “finger-print” approach to determine the lattice termination, e.g., in comparison to intensity calculations of ideally terminated lattices. We have provided a fundamental description of this phenomenon showing that it is general to layered crystals and is directly associated with the termination of the bulk lattice (i.e., “termination interference”). It is most visible for minerals that posses a center of symmetry when that symmetry is preserved when the bulk unit cell boundaries are determined by the terminating plane of the crystal. When this center of symmetry is missing (either because lattice termination, or because of an absence of such a symmetry in the bulk crystal structure) the ‘pseudo-nodes’ are much weaker. An approximate relation was developed to relate the terminating plane of the lattice to the pseudo-node location.
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