Density functional theory incorporating hybrid exchange–correlation functionals has been extraordinarily successful in providing accurate, computationally tractable treatments of molecular properties. However, conventional hybrid functionals can be problematic for solids. Their nonlocal, Hartree–Fock-like exchange term decays slowly and incorporates unphysical features in metals and narrow-bandgap semiconductors. This article provides an overview of our group’s work on designing hybrid functionals for solids. We focus on the Heyd–Scuseria–Ernzerhof screened hybrid functional [J. Chem. Phys. 2003, 118, 8207], its applications to the chemistry and physics of solids and surfaces, and our efforts to build upon its successes.

We propose a general model for the spherically averaged exchange hole corresponding to a generalized gradient approximation (GGA) exchange functional. Parameters are reported for several common GGAs. Our model is based upon that of Ernzerhof and Perdew [J. Chem. Phys. 109, 3313 (1998)]. It improves upon the former by precisely reproducing the energy of the parent GGA, and by enabling fully analytic evaluation of range-separated hybrid density functionals. Analytic results and preliminary thermochemical tests indicate that our model also improves upon the simple, local-density-based exchange hole model of Iikura et al. [J. Chem. Phys. 115, 3540 (2001)].

The ground state correlation energy of the random phase approximation from a ring coupled cluster doubles approach The Journal of Chemical Physics 129, 231101 (2008) We recently demonstrated a connection between the random phase approximation ͑RPA͒ and coupled cluster theory ͓G. E. Scuseria et al., J. Chem. Phys. 129, 231101 ͑2008͔͒. Based on this result, we here propose and test a simple scheme for introducing long-range RPA correlation into density functional theory. Our method provides good thermochemical results and models van der Waals interactions accurately.

Insight into the nature of transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions is obtainable from a number of surface spectroscopic techniques. Carrying out these investigations under actual reaction conditions is preferred but remains challenging, especially for catalytic reactions that occur in water. Here, we report the direct spectroscopic study of the catalytic hydrodechlorination of 1,1-dichloroethene in H2O using surface-enhanced Raman spectroscopy (SERS). With Pd islands grown on Au nanoshell films, this reaction can be followed in situ using SERS, exploiting the high enhancements and large active area of Au nanoshell SERS substrates, the transparency of Raman spectroscopy to aqueous solvents, and the catalytic activity enhancement of Pd by the underlying Au metal. The formation and subsequent transformation of several adsorbate species was observed. These results provide the first direct evidence of the room-temperature catalytic hydrodechlorination of a chlorinated solvent, a potentially important pathway for groundwater cleanup, as a sequence of dechlorination and hydrogenation steps. More broadly, the results highlight the exciting prospects of studying catalytic processes in water in situ, like those involved in biomass conversion and proton-exchange membrane fuel cells.

Semilocal density functional theory predictions for the barrier heights of representative hydrogen transfer, heavy-atom transfer, and nucleophilic substitution reactions are significantly improved in non-self-consistent calculations using Hartree-Fock orbitals. Orbitals from hybrid calculations yield related improvements. These results provide insight into compensating for one-electron self-interaction error in semilocal density functional theory.

Understanding the interactions of biomolecules with noble metal surfaces is critical to our development of functional biomedical nanodevices and accurate biosensors. Here we use surface enhanced Raman spectroscopy (SERS) and surface enhanced infrared absorption spectroscopy (SEIRA) on Au nanoshell substrates to study the interactions of adenine and two adenine derivatives, thiolated polyadenine single-stranded DNA (polyA) and adenosine monophosphate (AMP), with Au surfaces. pH-dependent conformational changes of these molecular species adsorbed on Au nanoshell surfaces were observed using SERS, and confirmed with SEIRA. The combined SERS-SEIRA spectra show significant pH dependence, consistent with adenine protonation and reduced Au-adenine binding at low pH. The spectra are also consistent with adenine binding "end-on" to the Au surface via a ring nitrogen, with the bond to the external NH 2 group aligned near the surface normal. For AMP, spectral evidence indicates binding through either a ring nitrogen and/or the external NH 2 group. Density functional calculations on adenine and comparisons with the literature allow us to assign the observed spectral features and to gain insight to the local binding geometry of the adsorbates.

Phosphinylidene compounds R(1)R(2)P(O)H are important functionalities in organophosphorus chemistry and display prototropic tautomerism. Quantifying the tautomerization rate is paramount to understanding these compounds' tautomerization behavior, which may impact their reactivities in various reactions. We report a combined theoretical and experimental study of the initial tautomerization rate of a range of phosphinylidene compounds. Initial tautomerization rates are found to decrease in the order H3PO2 > Ph2P(O)H > (PhO)2P(O)H > PhP(O) (OAlk)H > AlkP(O)(OAlk)H ≈ (AlkO)2P(O)H, where "Alk" denotes an alkyl substituent. The combination of computational investigations with experimental validation establishes a quantitative measure for the reactivity of various phosphorus compounds, as well as an accurate predictive tool.

Dissolution of lignocellulose in ionic liquids is a promising route to synthesizing fuels and chemical feedstocks from woody plant materials. While cellulose dissolution is well-understood, less is known about the differences between ionic liquids' interactions with cellulose vs. lignin. This work uses dispersion-corrected density functional theory (DFT-D) to model the interactions of imidazolium chloride ionic liquid anions and cations with (1,4)-dimethoxy-β-D-glucopyranose and 1-(4-methoxyphenyl)-2-methoxyethanol as models for cellulose and the lignin polyphenol, respectively. The cellulose model preferentially interacts with Cl(-), confirming previous experimental and theoretical studies. However, the lignin model has significant π-stacking and hydrogen bonding interactions with imidazolium cation. These results are robust to changes in the computational details, and suggest that the ionic liquid cations play important roles in tuning the relative solubilities of lignin and cellulose. Calculations predict that the extended π-systems of benzimidazolium ionic liquids yield stronger interactions with lignin, showing potential for improved lignocellulose solvents.