fix 2eorb

[jeffhammond]

2eorb has been busted for many methods in TCE for years. Fix it.

http://www.nwchem-sw.org/index.php/Special:AWCforum/st/id1755/#post_6665

[mattbernst]

I also made a compilation of broken 2eorb methods that used to work here: http://www.nwchem-sw.org/index.php/Special:AWCforum/st/id1775/many_TCE_methods_broken_with_2eo....html

The cc2, ccsd, ccsd(2)_t, ccsd(t), ccsd[t], cr-ccsd(t), cr-ccsd[t], lr-ccsd, and lr-ccsd(t) methods worked with 2eorb in 6.0 and still work in recent versions.

The ccsdt and cisdt methods worked with 2eorb in 6.0, but are marked incompatible with it in later versions.

The ccd, cisd, cr-qcisd(t), lccd, lccsd, lccsd(t), mbpt2, mbpt3, mbpt4, mbpt4(sdq), mbpt4sdq(t), qcisd, and qcisd(t) methods worked with 2eorb in 6.0, but crash with hashv2 errors in later versions.

[jeffhammond]

Thanks for the summary. If you bucket these methods, what you'll see is that the CCSD iterative code is fine, but everything else is broken. The (T) and related corrections are unaffected by this.

There are a few options here:

1. Implement the changes that were made in CCSD in all the iterative methods.
2. Bring back the working code from 6.0 for all the non-CCSD methods, which may lead to some near-duplication of methods.
3. Implement CCD, LCCD, LCCSD, and QCISD in terms of the CCSD code, which is possible but likely difficult to do correctly.
4. Remove CCD, LCCD, LCCSD, and QCISD, because there is no good reason to use them.

I am inclined to do 2 if it is less work than 1. Option 3 is too much work and option 4 is strictly academic.