Pentacene Multilayers on Ag(111) Surface

Abstract

The structural profiles and electronic properties of pentacene (C 22 H 14 ) multilayers on Ag(111) surface has been studied within the density functional theory (DFT) framework. We have performed first-principle total energy calculations based on the projector augmented wave (PAW) method to investigate the initial growth patterns of pentacene (Pn) on Ag(111) surface.In its bulk phase, pentacene crystallizes with a triclinic symmetry while a thin film phase having an orthorhombic unit cell is energetically less favorable by 0.12 eV/cell. Pentacene prefers to stay planar on Ag(111) surface and aligns perfectly along silver rows without any molecular deformation at a height of 3.9 Å. At one monolayer (ML) coverage the separation between the molecular layer and the surface plane extends to 4.1 Å due to intermolecular interactions weakening surface-pentacene attraction. While the first ML remains flat, the molecules on a second full pentacene layer deposited on the surface rearrange so that they become skewed with respect to each other. This adsorption mode is energetically more preferable than the one for which the molecules form a flat pentacene layer by an energy difference similar to that obtained for bulk and thin film phases. Moreover, as new layers added, pentacenes assemble to maintain this tilting for 3 and 4 ML similar to its bulk phase while the contact layer always remains planar. Therefore, our calculations indicate bulk-like initial stages for the growth pattern.

The role of the van der Waals interactions in the adsorption of anthracene and pentacene on the Ag(111) surface

“…6, in agreement with experimental observations 10,45,46 . Our results are also in good agreement with previous theoretical studies: from PBE calculations we found d = 3.938Å and E ads = −0.119 eV, which compare well with previous GGA results (d = 3.7-4.12Å and E ads within the range of −0.078 to −0.108 eV) 47,48 ; using the PBE+vdW surf method we found d = 2.910Å and E ads = −2.396 eV, which is in good agreement with previous results obtained by Toyoda et al 47 using the pairwise DFT-D method (d = 2.9Å and E ads = −2.28 eV), but differ from the values obtained by the same authors using the nonlocal vdW-DF method (d = 3.7Å and E ads = −1.62 eV) 47 . It should be pointed out that the vdW-DF method tends to overestimate the adsorption heights, even though it provides reliable adsorption energies 12,22 -recent vdW-DF functionals (e.g., optB86b-vdW and rev-vdW-DF2), however, have been shown to give both accurate adsorption height and energy 49 .…”

Understanding Charge Transfer in Donor–Acceptor/Metal Systems: A Combined Theoretical and Experimental Study

“…For example, when moving from a pure to a mixed donor/acceptor molecular monolayer on the same metal substrate. These systems have stimulated much interest for both experimentalists and theorists, particularly for olefins, 16 pentacene, [17][18][19][20][21][22][23][24] perfluorinated pentacene, [25][26][27] their 1:1 mixture, [28][29][30][31] copper phthalocyanine, [32][33][34][35][36][37] and fluorinated phthalocyanine, [38][39][40] on the (111) facet of the coinage metals. It has been repeatedly reported that such two-dimensional blending of donors and acceptors gives rise to core-level shifts in all atomic components.…”

Influence of substitution on the optical properties of functionalized pentacene monomers and crystals: Experiment and theory

“…The electronic structures of iodine-and rubidium-doped pentacene molecular crystals have also been investigated by ab-initio calculations based on the ultrasoft pseudopotential method, predicting a metallic behavior [19]. Recently, the structural and electronic properties of pentacene multilayers on the Ag(111) surface have been studied, revealing that pentacene has no electronic contribution at the Fermi level [20]. To describe the dielectric behavior, a general oscillator approach consisting of Gaussian peaks in the imaginary part of the dielectric function ε 2 (E) was applied (more detailed information about the fitting procedure and the Gaussian parameters can be found in the supporting information).…”