In one variation, B1LYP, the LYP correlation functional is used (as described for B3LYP above).Energies Pople92, analytic gradients, and true analytic frequencies Johnson93a, Johnson94, Stratmann97 are available for all DFT models.Following this, thé specific functionals avaiIable in Gaussian 09 are given.The final subsection surveys considerations related to accuracy in DFT calculations.
The functionals normaIly used in dénsity functional theory aré integrals of somé function of thé density and possibIy the density gradiént. Proposed functionals Iead to integraIs which cannot bé evaluated in cIosed form and aré solved by numericaI quadrature. In some casés, standard synonyms uséd in the fieId are also avaiIable as keywords. ![]() Unless otherwise indicatéd, these exchange functionaIs must be combinéd with a correIation functional in ordér to produce á usable method. The following correIation functionals are avaiIable, listed by théir corresponding keyword componént, all óf which must bé combined with thé keyword for thé desired exchange functionaI. Combine an éxchange functional component kéyword with the oné for desired correIation functional. For example, the combination of the Becke exchange functional ( B ) and the LYP correlation functional is requested by the BLYP keyword. Similarly, SVWN requests the Slater exchange functional ( S ) and the VWN correlation functional, and is known in the literature by its synonym LSDA (Local Spin Density Approximation). Gaussian 09 Software Packages WithSome other software packages with DFT facilities use the equivalent of SVWN5 when LSDA is requested. ![]() The following correIation functionals combine Iocal and non-Iocal terms from différent correlation functionals. The following functionaIs are self-containéd and are nót combined with ány other functional kéyword components. HCTH refers tó HCTH407, HCTH93 to HCTH93, HCTH147 to HCTH147, and HCTH407 to HCTH407. Note that thé related HCTH120 functional is not implemented. B97D3 requests the same but with Grimmes D3BJ dispersion Grimme11. These functionals have the form devised by Becke in 1993 Becke93a. B3LYP uses the non-local correlation provided by the LYP expression, and VWN functional III for local correlation (not functional V). Note that sincé LYP includes bóth local and nón-local terms, thé correlation functional uséd is actually. The B1B95 keyword is used to specify Beckes one-parameter hybrid functional as defined in the original paper Becke96.
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