title: Rare-earth vs. heavy metal pigments and their colors from first principles.
abstract: Many inorganic pigments contain heavy metals hazardous to health and environment. Much attention has been devoted to the quest for nontoxic alternatives based on rare-earth elements. However, the computation of colors from first principles is a challenge to electronic structure methods, especially for materials with localized f-orbitals. Here, starting from atomic positions only, we compute the colors of the red pigment cerium fluorosulfide as well as mercury sulfide (classic vermilion). Our methodology uses many-body theories to compute the optical absorption combined with an intermediate length-scale modelization to assess how coloration depends on film thickness, pigment concentration, and granularity. We introduce a quantitative criterion for the performance of a pigment. While for mercury sulfide, this criterion is satisfied because of large transition matrix elements between wide bands, cerium fluorosulfide presents an alternative paradigm: the bright red color is shown to stem from the combined effect of the quasi-2D and the localized nature of   states. Our work shows the power of modern computational methods, with implications for the theoretical design of materials with specific optical properties.
authors.affiliation: Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA. jtomczak@physics.rutgers.edu
authors.forename: Jan M
authors.initials: JM
authors.lastname: Tomczak
authors.forename: Leonid V
authors.initials: LV
authors.lastname: Pourovskii
authors.forename: Loig
authors.initials: L
authors.lastname: Vaugier
authors.forename: Antoine
authors.initials: A
authors.lastname: Georges
authors.forename: Silke
authors.initials: S
authors.lastname: Biermann
mesh_terms: D055592:Biophysical Phenomena; D002563:Cerium / Q000737:chemistry / Q000633:toxicity; D003116:Color; D004396:Coloring Agents / Q000737:chemistry* / Q000633:toxicity; D003460:Crystallization; D004563:Electrochemistry; D017669:Mercury Compounds / Q000737:chemistry / Q000633:toxicity; D019216:Metals, Heavy / Q000737:chemistry* / Q000633:toxicity; D008674:Metals, Rare Earth / Q000737:chemistry* / Q000633:toxicity; D008956:Models, Chemical; D055620:Optical Phenomena; D056951:Photoelectron Spectroscopy
chemical_list: D004396:Coloring Agents; D017669:Mercury Compounds; D019216:Metals, Heavy; D008674:Metals, Rare Earth; D002563:Cerium; C034211:cinnabar