Transformation Keyword
Last Update: 12/31/2000

This keyword controls the algorithm used for integral transformation, as well as the types of transformed integrals produced.

Direct Requests that the direct transformation routines be used. Equivalent to L804. Link 804 will select between the in-core, fully direct, and semi-direct methods automatically. This is the default.

InCore Forces use of the in-core algorithm in Link 804.

FullDirect Forces use of the fully direct (MO integrals in core) method in Link 804.

SemiDirect Forces use of the semi-direct algorithm in Link 804.

Conventional Requests that the original transformation method based on externally stored integrals be used. This was the only choice in Gaussian 90 and earlier versions. NoDirect is a synonym for Conventional.

Old2PDM Forces the old-fashioned process of the 2PDM in post-SCF gradients (sorted in L1111 and then processed in L702 and L703). This is slow, but it reduces memory requirements. This option cannot be used for frozen-core calculations.

New2PDM Causes the 2PDM to be generated, used, and discarded by L1111 in post-SCF gradient calculations. This is the default and fastest method, and it must be used for frozen-core calculations.

Full Forces a transformation over all orbitals (i.e., including transformed integrals involving all virtuals). ABCD is a synonym for Full.

IJAB Produce only <IJ||AB> integrals.

IAJB Produce <IJ||AB> and <IA||JB> integrals.

IJKL Produce <IJ||AB>, <IA||JB>, and <IJ||KL> integrals.

IJKA Produce <IJ||AB>, <IA||JB>, <IJ||KL>, and <IJ||KA> integrals.

IABC Produce <IJ||AB>, <IA||JB>, <IJ||KL>, <IJ||KA>, and <IA||BC> integrals.

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