JCP Communication 2015

 María Pilar de Lara-Castells*, Néstor F. Aguirre, Hermann Stoll, Alexander O. Mitrushchenkov, David Mateo, and Martí Pi. Communication: Unraveling the 4He-droplet mediated soft-landing from ab-initio-assisted and time-resolved density functional simulations.  The Journal of Chemical Physics (Comunications) 142 (2015) 131101.

An -based methodological scheme for He-surface interactions and zero-temperature time-dependent density functional theory for superfluid 4He droplets motion are combined to follow the short-time collision dynamics of the Au@4He system with the TiO(110) surface. This composite approach demonstrates the 4He droplet-assisted sticking of the metal species to the surface at low landing energy (below 0.15 eV/atom), thus providing the first theoretical evidence of the experimentally observed 4He droplet-mediated soft-landing deposition of metal nanoparticles on solid surfaces [Mozhayskiy , J. Chem. Phys. , 094701 (2007) and Loginov , J. Phys. Chem. A , 7199 (2011)].



María Pilar de Lara-Castells*, Hermann Stoll, Bartolomeo Civalleri, Mauro Causà, Elena Voloshina, Alexander O. Mitrushchenkov, and Martí Pi, Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of 4He nanodroplets on surfaces: 4He/graphene. Journal of Chemical Physics (Communications) 141, 151102 (2014).

In this work we propose a general strategy to calculate accurate He–surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on 4He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of 4He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the 4He nanodroplet (see figure below), the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.


Snapshots showing the temporal evolution of the 4He droplet at impact with the graphene surface. The display frames are 30 × 30 Å2. The axis (in Å) is oriented at the normal direction to the surface. The values of the densities (in Å−3) are given in the legends. Left-hand panel: dispersion-accounting dynamics. Right-hand panel: dispersionless dynamics. (Multimedia view). [URL:]