Study of the Quasi-Canonical Localized Orbital (QCLO) Method Based on Protein Structures

We have developed a density functional (DF) program, ProteinDF, for all-electron calculation on proteins. In order to overcome difficulties of a convergence problem in large-scale molecules, we have already proposed new localized orbital (LO), which named quasi-canonical LO (QCLO). In this study, improved convergence process which focused on the secondary structure such as hydrogen bonds and salt-bridge is proposed. The effectiveness of the improved process was discussed by comparing with the values of the original method, i.e. the total energy, convergence history and difference of Mulliken populations between initial and converged states. We proved the new convergence processes gave significantly better initial guess than previous one. This method could be useful for safe and automatic all-electron DF calculations on very large-scale proteins