For each atom there are a maximum of five one-center two-electron integrals.
These are
<*ss*|*ss*>,
<*ss*|*pp*>,
<*sp*|*sp*>,
<*pp*|*pp*>,
and
<*pp*|*p'p'*>,
where *p* and *p*' are two different *p*-type atomic orbitals.
In the original formulation [55] there was a sixth integral,
<*pp'*|*pp'*>,
but it can be shown that this integral is related to two of
the other integrals by:

<*pp*|*p'p'*> = 1/2( <*pp*|*pp*>
- <*pp*|*p'p'*>)

R(45^{o})*p _{x}* =
0.7071(

R(45^{o})*p*_{y} =
0.7071(*p*_{y}
- *p*_{x})

R(45^{o})*<p _{x}p_{y}|p_{x}p*

= 1/4(<*p*_{x}*p*_{x}|*p*_{x}
*p*_{x}>
+ <*p*_{y}
*p** _{y}*|

or

R(45^{o})*<p _{x}p_{y}|p_{x}p_{y}>*
= 1/2(<

For convenience these five integrals are given the following names:

<*ss*|*ss*> = G*ss
*<

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These expressions are common to all methods.