33 research outputs found
FDE-vdW: A van der Waals Inclusive Subsystem Density-Functional Theory
We present a formally exact van der Waals inclusive electronic structure
theory, called FDE-vdW, based on the Frozen Density Embedding formulation of
subsystem Density-Functional Theory. In subsystem DFT, the energy functional is
composed of subsystem additive and non-additive terms. We show that an
appropriate definition of the long-range correlation energy is given by the
value of the non-additive correlation functional. This functional is evaluated
using the Fluctuation-Dissipation Theorem aided by a formally exact
decomposition of the response functions into subsystem contributions. FDE-vdW
is derived in detail and several approximate schemes are proposed, which lead
to practical implementations of the method. We show that FDE-vdW is
Casimir-Polder consistent, i.e. it reduces to the generalized Casimir-Polder
formula for asymptotic inter-subsystems separations. Pilot calculations of
binding energies of 13 weakly bound complexes singled out from the S22 set show
a dramatic improvement upon semilocal subsystem DFT, provided that an
appropriate exchange functional is employed. The convergence of FDE-vdW with
basis set size is discussed, as well as its dependence on the choice of
associated density functional approximant
Derivation of the Supermolecular Interaction Energy from the Monomer Densities in the Density Functional Theory
The density functional theory (DFT) interaction energy of a dimer is
rigorously derived from the monomer densities. To this end, the supermolecular
energy bifunctional is formulated in terms of mutually orthogonal sets of
orbitals of the constituent monomers. The orthogonality condition is preserved
in the solution of the Kohn-Sham equations through the Pauli blockade method.
Numerical implementation of the method provides interaction energies which
agree with those obtained from standard supermolecular calculations within less
than 0.1% error for three example functionals: Slater-Dirac, PBE0 and B3LYP,
and for two model van der Waals dimers: Ne2 and (C2H4)2, and two model H-bond
complexes: (HF)2 and (NH3)2.Comment: 6 pages, 1 figure, REVTeX
Radiation chemistry of solid-state carbohydrates using EMR
We review our research of the past decade towards identification of radiation-induced radicals in solid state sugars and sugar phosphates. Detailed models of the radical structures are obtained by combining EPR and ENDOR experiments with DFT calculations of g and proton HF tensors, with agreement in their anisotropy serving as most important criterion. Symmetry-related and Schonland ambiguities, which may hamper such identification, are reviewed. Thermally induced transformations of initial radiation damage into more stable radicals can also be monitored in the EPR (and ENDOR) experiments and in principle provide information on stable radical formation mechanisms. Thermal annealing experi-ments reveal, however, that radical recombination and/or diamagnetic radiation damage is also quite important. Analysis strategies are illustrated with research on sucrose. Results on dipotassium glucose-1-phosphate and trehalose dihydrate, fructose and sorbose are also briefly discussed. Our study demonstrates that radiation damage is strongly regio-selective and that certain general principles govern the stable radical formation
Interaction energies in hydrogen-bonded systems: A testing ground for subsystem formulation of density-functional theory
Interaction between n-Alkane Chains: Applicability of the Empirically Corrected Density Functional Theory for Van der Waals Complexes
International audienc
Interaction energies in hydrogen-bonded systems: A testing ground for subsystem formulation of density-functional theory
The formalism based on the total energy bifunctional (E[rhoI,rhoII]) is used to derive interaction energies for several hydrogen-bonded complexes (water dimer, HCN–HF, H2CO–H2O, and MeOH–H2O). Benchmark ab initio data taken from the literature were used as a reference in the assessment of the performance of gradient-free [local density approximation (LDA)] and gradient-dependent [generalized gradient approximation (GGA)] approximations to the exchange-correlation and nonadditive kinetic-energy components of E[rhoI,rhoII]. On average, LDA performs better than GGA. The average absolute error of calculated LDA interaction energies amounts to 1.0 kJ/mol. For H2CO–H2O and H2O–H2O complexes, the potential-energy curves corresponding to the stretching of the intermolecular distance are also calculated. The positions of the minima are in a good agreement (less than 0.2 Å) with the reference ab initio data. Both variational and nonvariational calculations are performed to assess the energetic effects associated with complexation-induced deformations of molecular electron densities
NMR 13C chemical shift calculations of charged surfactants in water: a combined DFT and MD methodological study
International audienc
The effect of composition on optical and photocatalytic properties of novel visible light response materials Bi26-xMgxO40
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One-Electron Equations for Embedded Electron Density and Their Applications to Study Electronic Structure of Atoms and Molecules in Condensed Phase
Recent applications of one-electron equations for embedded electron density introduced originally for multi-level modeling of solvated molecules (T.A. Wesolowski, A. Warshel, J. Phys. Chem. 1993, 97, 8050) are reviewed. The considered applications concern properties directly related to the electronic structure of molecules (or an atom) in condensed phase such as: i) localized electronic excitations in a chromophore involved in a hydrogen-bonded intermolecular complex; ii) UV/Vis spectra of acetone in water; and iii) energy levels of f-orbitals for lanthanide cations in a crystalline environment. For each case studied, the embedding potential is represented graphically and its qualitative features are discussed