Electronic transport properties of compressed and stretched helicene-graphene nanostructures, a theoretical study

Abstract

We present our ab initio simulations of strained helicene molecular junction. First, we present ab-initio models of [n]helicenes up to [100]helicene done by two different recent reactive force field molecular geometry optimization methods (ReaxFF CHOCsKNaClIFLi, 2019 and CHONSMgPNaCuCl, 2018). We used the [4]helicene and [10]helicene models for Density Functional Theory (DFT) electronic transport calculations of various graphene-helicene-graphene molecular junction configurations on Local Density Approximation (LDA) or Generalized Gradient Approach (GGA) level of exchange and correlation energy with Perdew-Zinger (PZ) or Perdew–Burke–Ernzerhof (PBE) functionals and Grimme DFT-D3 van der Waals correction. The electronic transport properties are studied by using of the Green's functions formalism. The electron transmissions and densities of states of [4]helicene (and [10]helicene) attached as a molecular junction in three different configurations to zigzag graphene nanoribbon (ZGNR) electrodes of three different widths were obtained. The structures are analyzed while relaxed, compressed or stretched. The current-voltage and current-strain characteristics are presented and results are compared and discussed. The work is supported by a short review summarizing some of the recent studies related to graphene, helicene, and molecular junctions under strain.