Elk version 1.2.20 released

Dear All,

Elk version 1.2.20 has just been released.

The main changes have been in improving the BSE code: this now works
beyond the Tamm-Dankoff approximation.

Best wishes,
Kay Dewhurst, Sangeeta Sharma, Lars Nordstrom, Francesco Cricchio, Fredrik
Bultmark and Hardy Gross

-the Bethe-Salpeter equation (BSE) for linear optics now works beyond the
Tamm-Dankoff approximation
-RPA and BSE calculations now use full wavefunctions instead of plane waves
-removed the Coulomb regulator from the calculation of RPA dielectric
function, instead used the analytic results for the head and the wings of
the matrix (thanks to Vladimir Nazarov for discussions)
-improved the stability of radial Dirac and Schrodinger integrators
(thanks to Alexei Baranov, Frank Wagner and Ondrej Certik for discussions)
-added more block descriptions to the manual (thanks to various people for
pointing out omissions)
-various optimisations

Posted by John Kay Dewhurst 2011-03-17