`DH`, *ax*, *ac*

initiates a double-hybrid calculation (Ref. [1]) where is the fraction of HF exchange and is the fraction of MP2 correlation.
A self-consistent KS calculation is performed with functional
.
One then needs to call the MP2 program to add the MP2 contribution
. If is not given, is assumed, according to Ref. [2].

`DSDH`, *ax*, *ac*

initiates a density-scaled double-hybrid calculation (Ref. [2]) where is the fraction of HF exchange and is the fraction of MP2 correlation. A self-consistent KS calculation is performed with functional , where is the scaled density. In the case of meta-GGA functionals, the kinetic energy density is also scaled, according to Ref. [3]. One then needs to call the MP2 program to add the MP2 contribution . If is not given, is assumed, according to Ref. [2].

Example of input for B2-PLYP calculation (Ref. [1]):
`{ks,b,lyp;dh,0.53,0.27;}`
`mp2;`

Example of input for 1DH-BLYP calculation (Ref. [2]):
`{ks,b,lyp;dh,0.65;}`
`mp2;`

Example of input for DS1DH-TPSS calculation (Ref. [3]):
`{ks,tpss;dsdh,0.725;}`
`mp2;`

Unrestricted calculations (`uks`, `ump2`) can also be done.

References:

S. Grimme, J. Chem. Phys. **124**, 034108 (2006).

K. Sharkas, J. Toulouse, A. Savin, J. Chem. Phys. **134**, 064113 (2011).

S. M. O. Souvi, K. Sharkas, J. Toulouse, J. Chem. Phys. **140**, 084107 (2014).

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molpro@molpro.net 2018-06-20