Hybrid DFT functionals

The Onsager model describes the system as a molecule with a multipole moment inside of a spherical cavity surrounded by a continuum dielectric. In some programs, only a dipole moment is used so the calculation fails for molecules with a zero dipole moment. Results with the Onsager model and HF calculations are usually qualitatively correct. The accuracy increases significantly with the use of MP2 or hybrid DFT functionals. This is not the most accurate method available, but it is stable and fast. This makes the Onsager model a viable alternative when PCM calculations fail. 

Since a systematic study of this point is still missing, we investigated the performances of different computational approaches through geometry optimizations of the H2Si(Cp)2ZrCH3+ species with different pure and hybrid DFT functionals, and at the HF and MP2 level of theory. The main geometrical parameters are reported in Table 1. 

The GGA functionals just discussed are distinct from the hybrid DFT functionals that are widely preferred for DFT calculations of molecular systems.16,26 Hybrid functionals such as the B3LYP functional27 use a combination of exact Hartree-Fock exchange with GGA-based DFT functionals. This approach gives results that are in general more reliable than GGA functionals alone. Unfortunately, the exact exchange contributions are difficult to evaluate in plane wave basis sets,16 so the option of using hybrid DFT within plane wave calculations is not routinely available. Friesner recently reviewed the comparative performance of GGA and hybrid functionals, as well as other ab initio methods.16... 

CC-VSCF was also used for computing anharmonic vibrational spectra from DFT potentials [103,104], The most accurate spectroscopic results are obtained from the hybrid functionals B97 [105] and B3LYP [106], of the non-hybrid DFT functionals, HCTH [107] seems superior to BLYP [108], The spectroscopic accuracy of B97 and B3LYP was about equal to that of MP2. 

Trapped electron holes in MgO represent a typical electronic defect in a main group oxide, formed upon irradiation [138, 139] or aliovalent doping. They are experimentally well-characterised electronic defects in a host matrix, MgO, in which DFT is known to perform well. They represent therefore a suitable test to benchmark the ability of pure and hybrid DFT functionals in describing unpaired electrons in crystalline solids. 

LovaUo studied thermochemistry of organoxenon complexes [232] using the MP2 method and two hybrid DFT functionals together with the iMCPs. The following reactions were studied ... 

Miyoshi and co-workers carried out several studies related to adsorption. In an early study they modeled adsorption of SO2 on Ni(lll) and Cu(lll) surfaces [240] using a hybrid DFT functional and a mixed basis set (ECP [241] and cc-pVDZ [112]), followed by single-point energy evaluations at the CASSCF level with MCPs. For structural studies, Ni4S02 and Q14SO2 were chosen as model clusters to represent SO2 adsorbed on the metal M(lll) surfaces. Single-point... 

Yu, J. Balbuena, P. B. Budzien, J. Leung, K. Hybrid DFT Functional-Based Static and Molecular Dynamics Studies of Excess Electron in Liquid Ethylene Carbonate, J. Electrochem. Soc. 2011, 75S,A400-A410. 

The molecular calculations [550,560] allow us to conclude that the DKH approximation in combination with hybrid DFT functionals provides a reliable tool for the prediction of structural and thermochemical properties of molecules. 

Wilson and coworkers assessed the performance of 13 hybrid-GGA, hybrid-meta-GGA, and double-hybrid DFT functionals on the cc-CA-TM/11 dataset [83]. The hybrid B97-1 [42, 84] functional and the double-hybrid functional mPW2-PLYP [85] were found to give the best performance over experimental results with mean absolute deviations of 7.2 and 7.3 kcal mol . The dataset (cc-CA-TM/11) is rather diverse and consists of AyH of 193 3d transition metal molecules (Sc(C5H5)3 and (Cr03)3, halides, oxides, and heavy chalcogenides, hydrides, nitrides, small clusters, metal carbonyls, and other coordination complexes) [86]. 

In this contribution, we survey our recent theoretical work addressing the choice of the functional in density functional theory (DFT) to describe the charge-transfer character in the ground state of TTF/TCNQ model complexes [9, 10]. First, we examine how the nature of the functional impacts the electronic properties of isolated TTF or TCNQ molecules or stacks of each species. Through comparison to benchmark calculations, we then examine the impact of the functional choice on the computed charge transfer and associated interface dipole in TTF/TCNQ stacks. This smdy encompasses hybrid DFT functionals... 

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