Dimensionality effects on the electronic and structural properties of PtS 2 chains

Abstract

First-principles, density-functional methods are applied to study electronic and structural properties of infinite, periodic PtS 2 chains. Special emphasis is put on identifying those intra- and interchain interactions that are responsible for the electronic and the structural properties, respectively. Using a single-chain code we first study isolated planar and helical PtS 2 chains. Subsequently, the same method is applied in studying the chains when being surrounded by two K counterions per PtS 2 unit. Finally, we study the full three-dimensional crystal structure of K 2PtS 2 both without and with the K atoms. The results are compared with experimental information on crystalline materials containing PtS 2 chains surrounded by K, Na, or Rb counterions. Also the effects of spin–orbit couplings are examined. It is found that the neutral chains have structural properties different from the charged ones, but including the K atoms lead to a good agreement with experiment. Despite this, these chains are predicted to be metallic in contrast to experiment. The calculations on the crystalline compounds show that although the electronic interactions largely are confined to the individual chains, long-range Coulomb interactions change the materials from being metallic into being semiconducting. Finally, spin–orbit couplings have some effects on the structure and band structures, in particular for the planar conformation, but do hardly change the calculated structural properties.