Many‐body response of benzene at monolayer MoS₂: Van der Waals interactions and spectral broadening

Abstract

Models of surface enhancement of molecular electronic response properties are challenging for two reasons: (a) molecule-surface interactions require a simultaneous solution of the molecular and the surface dynamic response (a daunting task), and (b) when solving for the electronic structure of the combined molecule + surface system, it is not trivial to single out the particular physical effects responsible for enhancement. To tackle this problem, in this work, we apply a formally exact decomposition of the system's response function into subsystem contributions by using subsystem density functional theory (DFT), which grants access to dynamic polarizabilities and optical spectra. In order to access information about the interactions between the subsystems, we extend a previously developed subsystem-based adiabatic connection fluctuation-dissipation theorem of DFT to separate the additive from the nonadditive correlation energy and identify the nonadditive correlation as the van der Waals interactions. As an example, we choose benzene adsorbed on monolayer MoS 2. We isolate the contributions to benzene's dynamic response arising from the interaction with the surface, and for the first time, we evaluate the enhancements to the effectiveness of C 6 coefficients as a function of benzene-MoS 2 distance and adsorption site. We also quantify the spectral broadening of the benzene's electronic excited states due to their interaction with the surface. We find that the broadening has a similar decay law with the molecule-surface distance as the leading van der Waals interactions (ie, R −6) and that the surface enhancement of dispersion interactions between benzene molecules is less than 5% but is still large enough (0.5 kcal/mol) to likely play a role in the prediction of interface morphologies. K E Y W O R D S linear response, many body dispersion, TDDFT, van der Waals 1 | INTRODUCTION AND BACKGROUND The development of accurate models of materials' interfaces is a priority for materials science and engineering. [1,2] Interfaces are key regions in energy materials such as photovoltaics [3] and photocatalysts, [4] as well as in technological applications such as field-effect transistors. [5] Models must be accurate, in the sense that they need to at least reproduce the most basic of properties involved in the function of the material. These vary depending on the applications [6,7] ; however, properties such as the contact angle in a surface-water interface, [8] thermal transport in the material, [9] and the optical response [10] are among the ones widely sought after. An accurate model enables the rational design of materials, which

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“…Beside these applications, a vast array of chemical problems, for instance, solvation free energies, solvent effects on different types of spectroscopies, , magnetic properties, − charge-transfer states, − open-shell systems, and excited states, ,− have been explored by semilocal sDFT and its time-dependent extension. ,,, The fact that research continues to yield improved KEDFs suggests strongly that nonadditive KEDFs also will improve and, with that, the applicability of sDFT also will expand.…”

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“…By adopting these steps, eQE achieved high parallel efficiency as showcased in several application works [30,32,33,34]. We need to stress that the computational efficiency and accuracy of eQE is system dependent.…”

“…In the first release of eQE [26], we successfully implemented semilocal (GGA) level nonadditive functionals for both NAXC and NAKE with the following main features: (1) a scheme of parallel execution to distribute the workload across subsystems resulting in low data communication achieving high parallel efficiency, (2) ab initio molecular dynamics (AIMD), and (3) applicability to periodic systems. Many large systems currently outside KS-DFT's realm of applicability have been successfully studied by eQE [30,31,32,33,34,35,36]. eQE 2.0 is capable of deploying nonlocal and meta-GGA (mGGA) XC and NAKE functionals yielding highly accurate simulations of weakly interacting subsystems.…”

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“…This opens the door to the computation of subsystem quantities (such as spectra and polarizabilities [ 70,98,99 ] ) and how they are affected by the surrounding subsystems. [ 74,91 ] As shown by Umerbekova et al, [ 100 ] this has repercussions with regard to the design of force fields when the polarizabilities are evaluated at an imaginary frequency, yielding the van der Waals C 6 coefficients. [ 69,100,101 ] The contribution by Grimmel et al [ 102 ] shows that, within subsystem DFT, it is difficult to improve on the performance of the simple adiabatic local density approximation (ALDA) kernel for the nonadditive kinetic energy when considering its extensions to generalized gradient approximation (GGA) functionals.…”

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