--- Screened-exchange package (v6.11) ---

This is the ASA screened-exchange (SX) code adapted from Holger Rucker.
It is still under development.

The call entry is asasx, which executes the following flow :

    1.   Make the unscreened static response function P0 (asxp0).
         This is an asa-version: which means in this context,
         (a) "bare" potential V0 is just Madelung matrix + local terms
         (b) local term is a single number for each l.

    2.   Make the nonlocal, static screened W from P0 and V0 (wstat)

    3.   Subtract of the "local part" to W, done in one of two ways.
         (v1)  the local part of P0 is calculated, and W[ploc] taken
         for the static part
         (v2)  W(q->0) estimated assuming W(q) prop q**2.

    4.   Make Sigma(W) - Sigma(Wloc).  This is a perturbation correction

    5.   (Optional) inverse Bloch transform Sigma.

    6.   For each qp, add delta Sigma to potential, recalculate evals
         and evecs.

         Repeat steps 4,5,6 for niter times.

--- Additions to the input file ---
To create sigma, add token in category OPTIONS:

 SX= #, where # signifies:
     0 do nothing
     1 Create ASA SX Sigma
    11 Create ASA SX Sigma, including on-site interaction W

To read sigma and add to hamiltonian, add token in category HAM
 RDSIG= #
     0 do not read sigma or add to hamiltonian
     1 read sigma and add to hamiltonian
     2 read sigma, symmetrize it, and add to hamiltonian


 and optionally, a string with list of options separated by `;'

 SXOPTS= string[;string...]

         string:
         nit=#         iterates for sigma # times, updating sigma
                       with new evals but fixed P0.

--- Test cases ---
See file sx/README.