Difference between revisions of "CamCASP/Numerical"
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Integrals can be calculated using density-fitting (the default). But for a few kinds of 2-index integrals (nuclear, overlap, etc.) there is the possibility of calculating them without density-fitting. This can often be advantageous, in fact, for nuclear and overlap integrals, this is probably the thing to do whenever you can. |
Integrals can be calculated using density-fitting (the default). But for a few kinds of 2-index integrals (nuclear, overlap, etc.) there is the possibility of calculating them without density-fitting. This can often be advantageous, in fact, for nuclear and overlap integrals, this is probably the thing to do whenever you can. |
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| + | The energy modules all have the optional command |
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| − | The 4-index Coulomb integrals are robust (see |
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| + | INTEGRAL Switch = <switch> |
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| + | that can be used to set the method used to calculate the integrals. In general, ''Switch = 0'' means use density-fitting, and ''Switch = 1'' means use the exact evaluation (no density-fitting) if possible. Not all integrals can be evaluated without density-fitting. See '''df_integrals.F90''' for details. |
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| + | The 4-index Coulomb integrals are robust (see [[CamCASP/Programming/3 | Robust Integrals]] for details.). So these can be obtained quite accurately using density-fitting, i.e., |
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==Auxiliary Basis Sets== |
==Auxiliary Basis Sets== |
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Revision as of 10:54, 14 May 2009
CamCASP => Numerical Issues
Introduction
This page contains information related to the numerical accuracy of CamCASP.
Integral Switch
Integrals can be calculated using density-fitting (the default). But for a few kinds of 2-index integrals (nuclear, overlap, etc.) there is the possibility of calculating them without density-fitting. This can often be advantageous, in fact, for nuclear and overlap integrals, this is probably the thing to do whenever you can.
The energy modules all have the optional command
INTEGRAL Switch = <switch>
that can be used to set the method used to calculate the integrals. In general, Switch = 0 means use density-fitting, and Switch = 1 means use the exact evaluation (no density-fitting) if possible. Not all integrals can be evaluated without density-fitting. See df_integrals.F90 for details.
The 4-index Coulomb integrals are robust (see Robust Integrals for details.). So these can be obtained quite accurately using density-fitting, i.e.,
Auxiliary Basis Sets
MC or DC?
What sort of basis set