The c(4 × 2) structure of short- and intermediate-chain length alkanethiolate monolayers on Au(111): A DFT study

We report on first principles density functional theory calculations for a new adatom + vacancy model (ad+va) of the c(4 × 2) structure of short- and intermediate-length alkanethiolate self-assembled monolayers (SAMs) on Au(111). This model includes the same structural motif, two thiolates bound to an Au adatom and a surface vacancy, that has been recently proposed for the low-coverage and (√3 × √3)R30° phases of short-chain alkanethiolate SAMs on Au(111). We show that the ad+va model is more stable than all available (V√ × √3)R30° one-chain models and can also satisfactorily describe the experimental scanning tunneling microscopy images of the c(4 × 2) phase.