@@ -34,10 +34,7 @@ iteration rather than stored on disk.))
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At the heart of the SCF procedure is the expensive Fock-matrix term:
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- ```
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- EQUATION
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- F_{ij} = H^{\rm core}_{ij} + \sum_{kl}^{\rm AO} D_{kl} \left[ 2 (ij|kl) - (ik|jl) \right],
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- ```
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+ <img src =" ./figures/fock-matrix.png " height =" 50 " >
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where we use * i* , * j* , * k* , and * l* to denote AO-basis indices. As described
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in [ Project #3 ] ( https://github.com/CrawfordGroup/ProgrammingProjects/tree/master/Project%2303 ) , a simple algorithm for
@@ -117,44 +114,33 @@ each individual integral to the Fock matrix:
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iwl_buf_close(&InBuf, 1);
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```
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- Thus a given integral, (ij|kl), would contribute to **//at least two//** Fock matrix elements as:
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+ Thus a given integral, (ij|kl), would contribute to <b><i>at least two</i></b> Fock matrix elements as:
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+
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+ <img src="./figures/fock-contribution-1.png" height="25">
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- ```
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- EQUATION
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- F_ {ij} \leftarrow +2 * D_ {kl} (ij|kl)
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- ```
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and
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- ```
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- EQUATION
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- F_ {ik} \leftarrow - D_ {jl} (ij|kl).
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- ```
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+ <img src="./figures/fock-contribution-2.png" height="25">
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## Handling Permutational Symmetry
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The most difficult aspect of the out-of-core algorithm is the fact that file contains only the permutationally unique integrals,
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*(ij|kl)*, such that:
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- ```
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- EQUATION
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- i \geq j,\ \ \ \ \ k \geq l,\ \ \ \ \ \ {\rm and}\ \ \ \ \ \ ij \geq kl,
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- ```
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+
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+ <img src="./figures/index-restrictions.png" height="25">
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+
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where
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- ```
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- EQUATION
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- ij \equiv i(i+1)/2 + j\ \ \ \ \ \ {\rm and} \ \ \ \ \ \ kl \equiv k(k+1)/2 + l.
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- ```
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+ <img src="./figures/compound-indices.png" height="25">
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+
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Thus, when determining the contribution of a given integral to various elements
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of the Fock matrix, one must consider all possible unique permutations of the
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indices, *i*, *j*, *k*, and *l*. Note, however, that coincidences among the
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indices can limit the number of possibilities. For example, if one encountered
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- the integral *(22|11)*, it would contribute to a total of * ** four** * Fock
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+ the integral *(22|11)*, it would contribute to a total of <b><i> four</i></b> Fock
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matrix elements, viz.
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- ```
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- EQUATION
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- F_ {22} \leftarrow 2 D_ {11} (22|11),\ \ \ F_ {21} \leftarrow - D_ {21} (22|11),\ \ \ F_ {11} \leftarrow 2 D_ {22} (22|11),\ \ \ {\rm and}\ \ \ F_ {12} \leftarrow -D_ {12} (22|11).
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- ```
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+ <img src="./figures/fock-contribution-3.png" height="25">
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All such cases must be included in the algorithm to obtain a correct Fock matrix.
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