Atomic DFT

Density-Functional Theory. Transition metals pose a problem for classical quantum chemical methods like self-consistent field (SCF), perturbation theory, configuration interaction (Cl), and variations on these methods, because of the very large electron correlation. SCF underestimates binding substantially, and post-SCF methods are so expensive for transition metals that one can do a calculation only on models with few atoms. DFT on the other hand is relatively cheap it is about as expensive as SCF. Moreover, with the development of the generalized-gradient approximations it is also reasonably accurate. A large majority of quantum chemical... 

Exponents of a set of primitive Gaussian function have been optimized to yield the lowest pseudo atom energies for all first- and second-row elements with an atomic DFT code employing the appropriate GTH potential for each element. A family basis set scheme has been adopted using the same set of exponents for each angular momentum quantum number of the occupied valence... 

Fig. 3 Combining atomically resolved STEM EELS with modelling can reveal the bonding environment of individual atoms. DFT modelling of EELS near-edge fine structure shows that 3-fold coordinated Si impurities in graphene adopt a distorted, out of plane, geometry, while the bonding of 4-fold coordinated Si impurities is in-plane. Figure reprinted with permission from Q. M. Ramasse eta/.. Nano Lett., 2012, 13, 4989-4995. Copyright 2012 American Chemical Society.

The classical fluid systems are characterized with simplified Hamiltonian in which the semiempirical pairwise-additive interaction between two particles are included. Those semiempirical interactions substantially arise from the Pauh exclusion of two electrons at the same quantum state and from the electrostatic interactions among electrons and nuclei. As a result, both repulsion and attraction appear in the two-body interaction. Specifically, when all involved particles are spherical ones like atoms, ions, or coarsegrained beads, the systems are called simple fluids. Obviously, the pair interactions in simple fluid systems are simply distance-dependent. Toward the investigation of simple fluid systems, atomic DFT is developed. A notable merit of atomic DFT is that the contributions to the free energy functional from different interaction parts can be treated separately. To demonstrate, below we present the DFT investigations for the simple systems of HS fluids, LJ fluids, and charged systems. 

Because H2 can be modeled with spherical LJ particle, for those confined Fl2 systems in different MOFs materials, the local density p r) can be efficiently and accurately predicted by using atomic DFT as stated above (Liu et al., 2009). Besides, we also investigated the adsorptions ofFl2 in Zeo-litic imidazolate frameworks (ZIFs) (Liu, 2011). As shown in Fig. 22, the DFT predictions at three representative temperatures display very good agreement with simulation results. 

Although the employment of spherical LJ models for CO2, CH4, and N2 is not sufficiently accurate to quantify the absolute uptakes in a specific MOF framework, the separation behaviors of those gases can be well described. With this argument, we have studied (Liu et al., 2010b) the separation behavior of CO2/CH4 and CO2/N2 mixtures in Zn2 (BDC)2 (ted) and in ZIF-8 at room temperature by using atomic DFT. We predicted that... 

Table 1 Top 10 MOF Structures for Hj Adsorption Under Different Thermodynamic Conditions Predicted by Atomic DFT (Uptake Unit moi/L) 298 K, 0.1 MPa 298 K, 10 MPa 77 K, 0.1 MPa 77 K, 10 MPa ...

It should be mentioned atomic DFT has been widely apptied to characterize the pore size distribution of mesoporous and microporous materials. Such an interesting appHcation is initiatized by Quirke and his coworkers in 1989 by using local DFT (Seaton et al., 1989), and then carried out inde-pendendy by Lastoskie et al. (1993a, 1993b) and by Otivier (1995) with... 

The combination of DFT with simulation has been developed from various aspects. The famous combination is the Car—Parrinello QM/MM approach (Car and Parrinello, 1985) in which the QDFT is incorporated into MD simulation. Since its foundation, there is tremendous desire to perform mixed QM/MM (Burke, 2012). Regarding combination of polymeric DFT with simulation, it has been demonstrated that a single-chain simulation can be performed for collecting the intrachain correlation information, which is utilized in polymeric DFT for the investigation of polymer systems with finite chain concentration (Cao et al., 2006 Chen et al., 2008). In the following, we demonstrate two other examples on the combinations of atomic DFT and MDFT with simulation. 

Ligands Containing S and O or Se and O Donor Atoms. - The Raman spectra of LiAlCh/SOCh electrolyte solutions showed the presence of Li(S0Cl2)3 -.(S02)x+ and Li(SOCl2)/ species. IR data for ML (HL), where M = Li, Na or K, H2L = thiosalicylic acid, HL = l-nitroso-2-naphthol and related, show coordination of the thiosalicylic acid through S (of SH) and carbonyl O atoms." DFT calculations have been reported for the vibrational wavenumbers of SO c (x = 2 or 3) adsorbed on... 

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