Functional empirical

Each VSIE is a function (empirically established) of charge and electronic configuration the latter is obtained by Mulliken s population analysis ° conducted on the molecular orbitals. Therefore an iterative method is required. Each secular determinant is solved in cycles until self-consistent charge distribution is obtained. Some relation between the output from one iteration and the input from the next is often necessary to ensure convergence... 

Solan, M., Raffaelh, D. G., Paterson, D. M., White, P. C. L., Pierce, G. J., 2006. Theme section introduction—Marine biodiversity and ecosystem function empirical approaches and future research need. Marine Ecology Progress Series, 311, 175-178. 

A one-parameter hybrid functional combining the B88 exchange and B95 correlation has been proposed by Zhao et al. [247]. In another recent work, Zhao et al. [248] initiated the development of doubly hybrid functionals—empirical linear combinations of the Hartree-Fock, approximate DFT, and ab initio (e.g. MP2) energy terms. 

Three different approaches have been followed to solve this clue, and they form the backbones of all existing band-structure methods in terms of their nuclear potentials. Somewhat simplified, one may either ignore the core functions (empirical tight-binding approaches), one may modify the potential, thereby also ignoring the core functions (pseudopotential approach), or one may modify the basis sets and split the functions into core and beyond-core functions (cellular approaches and successors) [210]. 

The LDA and GGA functionals are both nonempirical functionals. Empirical functionals have also been proposed. Empirical functionals are fitted to selected experimental data and, therefore, contain a number of parameters that have been introduced and adjusted during the fitting process. 

Unfortunately, as with other measures of visual functions, empirical evidence for relationship between contrast sensitivity and actual driving behavior or crash involvement is quite weak (Charlton et al., 2004). When a relationship is obtained it is mostly in older drivers who often suffer from a host of other visual and attentional problems (Decina and Staplin, 1993 Owsley et al., 1998,2001 see also Chapter 7). 

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