The Augmented Roothaan-Hall Direct Inversion Iterative Subspace (ADIIS) scheme by Xiangqian Hu and Weitao Yang, J. Chem Phys 132, 054109 (2010) has now been implemented in ADF. According to preliminary tests, this algorithm performs much better than Energy-DIIS. Additionally, unlike EDIIS, ADIIS does not require calculation of the total energy, so it is much faster. The ADIIS scheme in ADF has also been extended to support relativistic Spin-Orbit SCF calculations.
The cobalt-centered molecule to the left is the central region of the B-12 vitamin. With the new ADIIS option enabled the SCF for this molecule converges in 52 steps at the LDA/TZP level. Without ADIIS no convergence could be obtained due to the small HOMO-LUMO gap (~10meV) of the system.
This feature is now available in the development snapshots of ADF, versions r23063 and later, as well as in the Fix2009 snapshots, version r23064 and later. They can be downloaded at http://www.scm.com/SCMForms/DownloadSnapshots.jsp and http://www.scm.com/SCMForms/DownloadSnapshots.jsp?branch=fix2009, respectively. The text for the usage of ADIIS can be found in the developer’s change-log at: http://www.scm.com/Downloads/ChangeLog-trunk.html.