Add shorthand for SPW92 functional

[susilehtola]

Description

Adds shorthand for SPW92 functional. Also removes a spurious citation from SVWN.

User API & Changelog headlines

• RN 1
• RN 2

Dev notes & details

• Calculations can be launched with SPW92.

Questions

• Can someone add in the test reference energies? I don't have a running version of Psi4...

Checklist

• Tests added for any new features
• All or relevant fraction of full tests run

Status

• Ready for review
• Ready for merge

[loriab]

Thanks for the fctl. These are the values I generate

E18 = -74.736724053      #TEST
E28 = -74.736724053      #TEST
E38 = -74.387079031      #TEST
E48 = -74.213835345      #TEST

[loriab]

Thanks for the functional and cleanup. Here's the citations I'm getting now for the LDA functionals.

   => Composite Functional: SVWN <=

    Slater exchange
    Vosko, Wilk & Nusair (VWN5_RPA)
    P. A. M. Dirac, Math. Proc. Cambridge Philos. Soc. 26, 376 (1930) (10.1017/S0305004100016108)
    F. Bloch, Z. Phys. 57, 545 (1929) (10.1007/BF01340281)
    S. H. Vosko, L. Wilk, and M. Nusair, Can. J. Phys. 58, 1200 (1980) (10.1139/p80-159)

   => Composite Functional: SPW92 <=

    Slater exchange
    Perdew & Wang
    P. A. M. Dirac, Math. Proc. Cambridge Philos. Soc. 26, 376 (1930) (10.1017/S0305004100016108)
    F. Bloch, Z. Phys. 57, 545 (1929) (10.1007/BF01340281)
    J. P. Perdew and Y. Wang, Phys. Rev. B 45, 13244 (1992) (10.1103/PhysRevB.45.13244)