title: Computational study of the structure of a sepiolite/thioindigo mayan pigment.
abstract: The interaction of thioindigo and the phyllosilicate clay sepiolite is investigated using density functional theory (DFT) and molecular orbital theory (MO). The best fit to experimental UV/Vis spectra occurs when a single thioindigo molecule attaches via Van der Waals forces to a tetrahedrally coordinated Al(3+) cation with an additional nearby tetrahedrally coordinated Al(3+) also present. The thioindigo molecule distorts from its planar structure, a behavior consistent with a color change. Due to the weak interaction between thioindigo and sepiolite we conclude that the thioindigo molecule must be trapped in a channel, an observation consistent with previous experimental studies. Future computational studies will look at the interaction of indigo with sepiolite.
authors.affiliation: Materials Research and Technology Institute, The University of Texas at El Paso, El Paso, TX 79912, USA.
authors.forename: Manuel
authors.initials: M
authors.lastname: Alvarado
authors.forename: Russell C
authors.initials: RC
authors.lastname: Chianelli
authors.forename: Roy M
authors.initials: RM
authors.lastname: Arrowood