Dielectric properties of metallic nanosystems from second-principles computations

__A. Cloots^{1}__, L. Henrard

*, X. Gonze*

^{2}

^{1,3}^{1}*Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Belgium
^{2}*

*Département de Physique*,

*Université de Namur, Belgium*

^{3}*Skolkovo Institute of Technology, Moscow, Russia*

*alexandre.cloots@uclouvain.be*

Surface-Enhanced Vibrational Spectroscopy (SEVS) is a powerful tool to characterize molecules [1]. Due to its numerous advantages (non-destructive, ultra-high energy resolution, identification capabilities, etc.), it is widely used as sensing of systems in fields ranging from polymer sciences to biochemistry. Due to the combined need to describe a molecule and the enhancing surface (usually a metallic nanoparticle with much over thousands of atoms), the accurate simulation of SEVS is a challenge.

This is the problem addressed by the SURFASCOPE project. In the frame of this project, one of the most important issue that must be tackled is the computation of the dielectric response of a metallic nanoparticle to which a molecule is close. These are key elements of SEVS as they are responsible for the high enhancement factor of this kind of experiment. Classical models are often used to simulate the dielectric response of the metallic system but none of them are sufficient to answer all the questions about the interpretation of the experimental data [2]. Moving to first-principles computation might help to better understand the various phenomena occurring during the SEVS. However, this type of technique requires an increasing amount of time as the size of the system increases making it impractical to simulate systems of thousands of atoms (about the size of small nanoparticles). Therefore second-principles methods (i.e., methods building up on several first-principles computations [3]) might become handy, allowing one to preserve the accuracy of the first-principles computations while keeping the time required to perform the computation to its minimum.

In this poster, we will present different ways to derive dielectric properties of metallic nanoparticles from second-principles. The function of interest will be the density response function as it is a central quantity in this frame and can easily be derived from first-principles computations (e.g., via Adler-Wiser formula [4-5] in the frame of GW computations). The poster will present how, by working on a few relatively small unit cells (primitive or slab models), one can recover the properties of larger systems, and point out difficulties and solutions.

[1] B. Sharma, R. Frontiera, A.-I. Henry, E. Ringe, and R. Van Duyne, Materials Today **15**, 1369-7021 (2012).

[2] S. Wasserroth, T. Bisswanger, N. Mueller, P. Kusch, S. Heeg, N. Clark, F. Schedin, R. Gorbachev, and S. Reich, Phys. Rev. B 97, 155417 (2018)

[3] P. García-Fernández, J. Wojdeł, J. Íñiguez, J. Junquera, Phys. Rev. B **93**, 195137 (2016)

[4] L. Adler, Phys. Rev. **126**, 413—420 (1962)

[5] N. Wiser, Phys. Rev. **129**, 62—69 (1963)