In this section we describe the parameters most relevant to the accuracy and performance of the PNO program. We note that our team has carefully selected the default options through benchmark calculations, and the options only need to be modified for special cases.

Options for **PAO/OSV/PNO generation**:

`THRNPA`=*value*- Charge threshold for selection of primary PAO domains when using IBOs or NBOs (default 0.2).
`IEXT`=*value*- Domain extension using connectivity.
*value*corresponds to the number of bonds by which the primary domains are extended. The default is`IEXT=2`. `REXT`=*value*- Domain extension using distance.
*value*is the radius in from any atom in the primary domain.`IEXT`and`REXT`can be combined. If both are given all atoms are included that are selected by one or the other criterion. The default is`REXT=5`. `THROSV`=*threshold*- OSV selection threshold based on occupation numbers (default 1.d-9).
`THRPNO`=*threshold*- PNO selection threshold based on the energy criterion (default 0.998). If
*thresh*is smaller than 0.1 it refers to the natural occupation numbers, otherwise it refers to the fraction of OSV pair energies to be recovered. It is also possible to specify 3 values for strong+close, weak, and distant pairs as`THRPNO`=[*thrstrong, thrweak, thrdist*]. `THRPNO_OCC`=*threshold*- PNO selection threshold based on occupation numbers (default 1.d-8). If
`THRPNO`is also given, a PNO is selected only when both criteria are fulfilled.

Options for **F12 calculations**:

`BB_F12`- (logical). If true use the local and parallel F12 energy routines (default
`.true.`). Otherwise F12 routines relying on hard disk I/O (and therefore shall be run on a single computer node) will be used. This option shall only be set false if problems (such as insufficient memory available) arise from the parallel F12 routines. `BB_F12_PNO`=*value*- If
`BB_F12_PNO`=0, both OSV- and PNO-LMP2-F12 energy will be computed; If`BB_F12_PNO`=1, only PNO-LMP2-F12 energy will be computed; If`BB_F12_PNO`=2, only OSV-LMP2-F12 correction will be computed and the resulting energy will be set to PNO-LMP2 energy plus OSV-LMP2-F12 correction (default 1). `THRF12`=*threshold*- LMP2 pair energy threshold for selecting pairs for which F12 corrections are computed. The default value is 1.d-4.

Options for **domain approximations and orbital screening**:

`LOCFIT=0`- Disables local fitting (default is
`LOCFIT=1`). `IDFDOM`=*value*- Fitting domain extension using connectivity. The default is 3.
`RDFDOM`=*value*- Fitting domain extension using distances in . The default is 7. If both
`IDFDOM`and`RDFDOM`are given, the DF functions at a center will be included when either criterion is fulfilled. `LOCRI=0`- Disables local RI (default is
`LOCRI=1`). `IRIDOM`=*value*- RI domain extension using connectivity. The default is 3.
`RRIDOM`=*value*- RI domain extension using distances in . The default is 7. If both
`IRIDOM`and`RRIDOM`are given, the RI basis functions at a center will be included when either criterion is fulfilled. `FITLMO`=*threshold*- In the PNO program LMOs are truncated if the square sum of the coefficients at one center is smaller than
*threshold*(default 1.d-6). The remaining LMO coefficients are fitted to the original LMO. `FITPAO`=*threshold*- In the PNO program PAOs at one center are truncated when none of the PAOs at the center has a square sum of coefficients greater than
*threshold*(default 1.d-6). The remaining PAO coefficients are fitted to the original PAOs. `BB_F12_THRVAL`=*value*- The MP2 pair energy threshold in determining the LMO domains used in the F12 strong orthogonality projector (default 1.d-4). This option only applies to the selection of the valence occupied orbitals in the LMO domains.
`ICOREDOM_F12`=*value*,`RCOREDOM_F12`=*value*- The connectivity and distance (in ) criteria in determining the LMO domains used in the F12 strong orthogonality projector (defaults are 2 and 5.0, respectively). This option only applies to the selection of the core orbitals in the LMO domains.

Options for **symmetry**:

`LOCSYM=1`- Use point group symmetry (default is
`LOCSYM=0`). Note that the PNO-LMP2-F12 program does not support point group symmetry.

manual quickstart instguide update basis

molpro@molpro.net 2018-06-18