#GAUSSIAN SOFTWARE DENSITY PLUS#

Where E X is the exchange functional, and E C is the correlation functional. In the Kohn-Sham formulation of density functional theory, the exact exchange (HF) for a single determinant is replaced by a more general expression, the exchange-correlation functional, which can include terms accounting for both the exchange and the electron correlation energies, the latter not being present in Hartree-Fock theory:Д® KS = V + вџЁhPвџ© + 1/2вџЁPJ(P)вџ© + E X + E C The exchange energy resulting from the quantum (fermion) nature of electrons. The classical coulomb repulsion of the electrons.

#GAUSSIAN SOFTWARE DENSITY PLUS#

The one-electron (kinetic plus potential) energy. Where the terms have the following meanings: V In Hartree-Fock theory, the energy has the form:Д® HF = V + вџЁhPвџ© + 1/2вџЁPJ(P)вџ© вЂ“ 1/2вџЁPK(P)вџ© An alternate grid may be selected with the Integral=Grid option in the route section. tight geometry optimizations of certain kinds of systems). Larger grids are available when needed (e.g. Note also that it is important to use the same grid for all calculations where you intend to compare energies (e.g., computing energy differences, heats of formation, and so on). We do not recommend using any smaller grid in production DFT calculations. This grid greatly enhances calculation accuracy at reasonable additional cost. The UltraFine integration grid (corresponding to Integral=UltraFine) is the default in Gaussian 16. Thus in addition to the sources of numerical error in Hartree-Fock calculations (integral accuracy, SCF convergence, CPHF convergence), the accuracy of DFT calculations also depends on the number of points used in the numerical integration. This step is a numerical integration of the functional (or various derivatives of the functional). Accuracy ConsiderationsДЄ DFT calculation adds an additional step to each major phase of a Hartree-Fock calculation. Note: The double hybrid functionals are discussed with the MP2 keyword since they have similar computational cost. Polarizability derivatives (Raman intensities) and hyperpolarizabilities are not computed by default during DFT frequency calculations. The same optimum memory sizes given by freqmem are recommended for DFT frequency calculations. See the discussion in Basis Sets for details. Pure DFT calculations will often want to take advantage of density fitting. The self-consistent reaction field ( SCRF) can be used with DFT energies, optimizations, and frequency calculations to model systems in solution. Energies, analytic gradients, and true analytic frequencies are available for all DFT models. Gaussian 16 offers a wide variety of Density Functional Theory (DFT) models (see also for discussions of DFT methods and applications).

Gaussian software density