Understanding the Phase Diagram of Self-Assembled Monolayers of Alkanethiolates on Gold
Journal article, 2016

Alkanethiolate monolayers on gold are important both for applications in nanoscience as well as fundamental studies of adsorption and self-assembly at metal surfaces. While considerable experimental effort has been put into understanding the phase diagram of these systems, theoretical work based on density functional theory (DFT) has long been hampered by the inability of conventional exchange-correlation functionals to describe dispersive interactions. In this work, we combine dispersion-corrected DFT calculations using the new vdW-DF-CX functional with the ab initio thermodynamics method to study the stability of dense standing-up and low-coverage lying-down phases on Au(111). We demonstrate that the lying-down phase has a thermodynamic region of stability starting from thiolates with alkyl chains consisting of n ? 3 methylene units. This phase emerges as a consequence of a competition between dispersive chain-chain and chain-substrate interactions, where the strength of the latter varies more strongly with n. A phase diagram is derived under ultrahigh-vacuum conditions, detailing the phase transition temperatures of the system as a function of the chain length. The present work illustrates that accurate ab initio modeling of dispersive interactions is both feasible and essential for describing self-assembled monolayers.

Author

Joakim Löfgren

Chalmers, Physics, Materials and Surface Theory

Henrik Grönbeck

Chalmers, Physics, Chemical Physics

Kasper Moth-Poulsen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

Paul Erhart

Chalmers, Physics, Materials and Surface Theory

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 120 22 12059-

Single Molecule Nano Electronics (SIMONE)

European Commission (FP7), 2014-02-01 -- 2019-01-31.

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Materials Science

Subject Categories

Materials Engineering

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

DOI

10.1021/acs.jpcc.6b03283

More information

Latest update

5/17/2018