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Quantitative prediction of optical absorption in molecular solids using an optimally tuned screened range-separated hybrid functional


  Arun K. Manna [1]  ,  Sivan Refaely-Abramson [1,2]  ,  Anthony M. Reilly [3]  ,  Alexandre Tkatchenko [4]  ,  Jeffrey B. Neaton [2]  ,  Leeor Kronik [1]  
 [1] Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel
[2] Department of Physics, University of California, Berkeley, CA 94720-7300, USA
[3] The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England
[4] Physics and Materials Science Research Unit, University of Luxembourg, L-1511, Luxembourg

Quantitative prediction of optical absorption in the solid-state using density functional theory (DFT) is a long-standing challenge. In principle, this should be possible with time-dependent DFT (TDDFT). In practice, the results depend very strongly on the approximate exchange-correlation functional. Standard approximations, even ones that work well for many molecular systems, usually fail qualitatively in the solid state. 

We show that such prediction is in fact possible, using the recently-developed time-dependent optimally-tuned screened range-separated hybrid (OT-SRSH) [1,2]. Briefly, in this method the molecular electronic structure is determined by optimal tuning of the range-separation parameter in a range-separated hybrid functional. Then, electronic screening and polarization in the solid-state are taken into account by adding long-range dielectric screening to the functional form.

We provide a comprehensive benchmark for the accuracy of this approach, by considering the X23 benchmark set of molecular solids [3], with structures obtained using a semi-local exchange-correlation functional PBE, augmented with pairwise dispersion interactions as prescribed by Tkatchenko and Scheffler [4], and a dielectric constant obtained from both many-body dispersion and the random-phase approximation. We find our results to be in good agreement with many-body perturbation theory in the GW-BSE approximation [5]. We discuss strengths and weaknesses of the approach. We believe that it could be used for studies of molecular solids typically outside the reach of computationally more intensive methods.

References: 

1. S. Refaely-Abramson, M. Jain, S. Sharifzadeh, J. B. Neaton, L. Kronik, “Solid-state optical absorption from optimally tuned time-dependent range-separated hybrid density functional theory”, Phys. Rev. B (Rapid Comm.) 92, 081204(R) (2015).

2. L. Kronik and J. B. Neaton, “Excited State Properties of Molecular Solids from First Principles”, Annual Reviews Phys. Chem. 67, 587 (2016).

3. A. M. Reilly and A. Tkatchenko, “Understanding the role of vibrations, exact exchange, and many-body van der Waals interactions in the cohesive properties of molecular crystals”, J. Chem. Phys. 139, 024705 (2013).

4. A. Tkatchenko, M. Scheffler, “Accurate molecular van der Waals interactions from ground-state electron density and free-atom reference data”, Phys. Rev. Lett. 102, 73005 (2009).

5. A. K. Manna, S. Refaely-Abramson, A. M. Reilly, A. Tkatchenko, J. B. Neaton, and L. Kronik, “Quantitative prediction of optical absorption in molecular solids using an optimally tuned screened range-separated hybrid functional” (manuscript in preparation).