Gaussian 03 Online Manual
Last update: 2 October 2006

Frozen Core Options

These options specify which inner orbitals are frozen in post-SCF calculations. Gaussian 03 adds some additional options to the ones already available in the program [489].

FC
This indicates "frozen-core," and it implies that inner-shells are excluded from the correlation calculation. This is the default calculation mode. Note that FC, Full, RW and Window are mutually exclusive. It is which is equivalent to FreezeG2 for the 6-31G and 6-311G basis sets and to FreezeNobleGasCore for all other basis sets, except that the outer s and p core orbitals of 3rd row and later alkalai and alkalai earth atoms are not frozen (in accord with the G2/G3 conventions).

FreezeNobleGasCore

In post-SCF calculations the largest noble gas core is frozen. FrzNGC is a synonym for this option.

FreezeInnerNobleGasCore

In post-SCF calculations, the next to largest noble gas core is frozen. That is, the outermost core orbitals are retained. FrzINGC and FC1 are synonyms for this option.

FreezeG2
Freeze orbitals according to the G2 convention: d orbitals of main group elements are frozen, but the outer sp core of 3rd row and later alkalai and alkalai earth elements are kept in the valence.

Full
This specifies that all electrons be included in a correlation calculation.

RW
The "read window" option means that specific information about which orbitals are retained in the post-SCF calculation will be given in the input file. The additional input section consists of a line specifying the starting and ending orbitals to be retained, followed by a blank line. A value of zero indicates the first or last orbital, depending on where it is used. If the value for the first orbital is negative (-m), then the highest m orbitals are retained; if the value for the last orbital is negative (-n), then the highest n orbitals are frozen. If m is positive and n is omitted, n defaults to 0. If m is negative and n is omitted, then the highest |m| occupied and lowest |m| virtual orbitals are retained.

Here are some examples for a calculation on C₄H₄:

0,0 is equivalent to Full.

5,0 freezes the 4 core orbitals and keeps all virtual orbitals (equivalent to FC if the basis has a single zeta core).

5,-4 freezes the four core orbitals and the highest four virtual orbitals. This is the appropriate frozen-core for a basis with a double-zeta core.

6,22 retains orbitals 6 through 22 in the post-SCF. For example, since C₄H₄ has 28 electrons, if this is a closed shell calculation, there will be 14 occupied orbitals, 5 of which will be frozen, so the post-SCF calculation will involve 9 occupied orbitals (orbitals 6-14) and 8 virtual orbitals (orbitals 15-22).

-6 retains orbitals 9 through 20.

ReadWindow is a synonym for RW.

Window=(m[,n])
Performs the same function as the ReadWindow option, but takes its input as parameters in the route section rather than from the input stream.

ChkWindow
The window read in during a previous job is recovered from the checkpoint file.

ListWindow
Causes a list of orbitals to freeze (omit from post-SCF calculations) to be read from the input stream, terminated by a blank line. Two lists are read for unrestricted calculations. A range of orbitals can be specified, e.g.: 2 7-10 14