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the_density_functional_program [2023/09/18 15:34] – [Note on Minnesota Density Functionals] hesselmannthe_density_functional_program [2024/01/27 11:33] (current) – [Empirical damped dispersion correction] hesselmann
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 Grid points very close to the nucleus can have very small grid weights which can drop below machine precsion (~10d-16) when the radial grid is very large. These can be discarded with the option ''WEIGHT_CUT''=//thr//, i.e., grid points with weights smaller than //thr// will then not be used in the numerical integration anymore. While this can make the integration a little bit more efficient, a truncation of the grid with this option can prevent to achieve high accuracies in the numerical integration below, e.g., micro-hartree accuracies for energies. Therefore by default ''WEIGHT_CUT'' is set to a very small number that is well below machine precision (''WEIGHT_CUT''=1d-20) so that effectively all grid points close to the nucleus are taken into account for the integration.  Grid points very close to the nucleus can have very small grid weights which can drop below machine precsion (~10d-16) when the radial grid is very large. These can be discarded with the option ''WEIGHT_CUT''=//thr//, i.e., grid points with weights smaller than //thr// will then not be used in the numerical integration anymore. While this can make the integration a little bit more efficient, a truncation of the grid with this option can prevent to achieve high accuracies in the numerical integration below, e.g., micro-hartree accuracies for energies. Therefore by default ''WEIGHT_CUT'' is set to a very small number that is well below machine precision (''WEIGHT_CUT''=1d-20) so that effectively all grid points close to the nucleus are taken into account for the integration. 
-==== Grid caching (GRIDSAVE, NOGRIDSAVE) ==== 
- 
-''NOGRIDSAVE'' 
- 
-disables the disk caching of the grid, i.e, forces the recalculation of the grid each time it is needed. 
- 
-''GRIDSAVE'' 
- 
-forces the use of a grid cache where possible. 
  
 ==== Grid symmetry (GRIDSYM,NOGRIDSYM) ==== ==== Grid symmetry (GRIDSYM,NOGRIDSYM) ====
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 Gradient contributions from the D3 and D4 dispersion correction are automatically computed in DFT geometry optimisations. Gradient contributions from the D3 and D4 dispersion correction are automatically computed in DFT geometry optimisations.
 +
 +Note that not all functionals implemented in Molpro (and Libxc) are known to the D4 program (and vice versa). And in some cases the functionals supported by D4 might have a different identifier than used in Molpro. To see which functionals can be used with D4, see the documentation at [[https://github.com/dftd4/dftd4]]. Most functionals supported by D4 can also be given by their Libxc names, for example
 +<code> ks,gga_x_b88,gga_c_p86,disp=d4 </code>
 +using the ''B88'' exchange and ''P86'' correlation functional names as defined in the Libxc library. For compound functionals like B+P86 it is important to //insert the exchange functional first and the correlation functional second//!
 +
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 References:\\ References:\\