01939nas a2200169   4500008004100000245012400041210006900165260000800234300001400242490000800256520129700264100001901561700002001580700002101600700002601621856012201647       2009                        eng d00aAccelerating convergence in iterative solution for large-scale complete active space self-consistent-field calculations0 aAccelerating convergence in iterative solution for largescale co  cAUG  a2178-21900 v1093 aAn algorithm that accelerates the convergence of the iterative optimization of the complete active space self-consistent field (CASSCF) wavefunction so as to find a optimum solution in fewer macroiterations is described. The algorithm is oriented to large-scale CASSCF problems that are to be solved with a combination of density matrix renormalization group (DMRG) method for the configuration interaction (CI) process. The algorithm is based on the alternating (or two-step) CASSCF optimization in which the CI and molecular orbital (MO) parameters are optimized separately. Convergence ratio is improved by finding further optimized MOs from a linear extrapolation of the MO sets of the iteration history. The acceleration results in fewer diagonalizations in a total CASSCF calculation to save a considerable computational cost. The convergence performance is examined in a couple of realistic applications on SiC(3) and poly (phenyl)carbenes. For poly(phenyl)carbenes, the large-size CASSCF calculations with CAS(30e,30o) that entails full pi valence space as well as sp(2) orbital space of carbenes are performed by using the practical implementation of DMRG-CASSCF in conjunction with the acceleration technique. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 2178-2190, 20091 aYanai, Takeshi1 aKurashige, Yuki1 aGhosh, Debashree1 aChan, Garnet, Kin-Lic  uhttps://library.ncl.res.in/content/accelerating-convergence-iterative-solution-large-scale-complete-active-space-self02230nas a2200253   4500008004100000245008600041210006900127260000800196300001200204490000800216520142300224100001601647700001901663700002401682700002701706700002001733700002001753700002201773700001701795700001401812700001801826700002101844856011101865       2015                        eng d00aAdvances in molecular quantum chemistry contained in the Q-Chem 4 program package0 aAdvances in molecular quantum chemistry contained in the QChem 4  cJAN  a184-2150 v1133 a<p>A summary of the technical advances that are incorporated in the fourth major release of the Q-Chem quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation theories, methods for electronically excited and open-shell species, tools for treating extended environments, algorithms for walking on potential surfaces, analysis tools, energy and electron transfer modelling, parallel computing capabilities, and graphical user interfaces. In addition, a selection of example case studies that illustrate these capabilities is given. These include extensive benchmarks of the comparative accuracy of modern density functionals for bonded and non-bonded interactions, tests of attenuated second order Moller-Plesset (MP2) methods for intermolecular interactions, a variety of parallel performance benchmarks, and tests of the accuracy of implicit solvation models. Some specific chemical examples include calculations on the strongly correlated Cr-2 dimer, exploring zeolite-catalysed ethane dehydrogenation, energy decomposition analysis of a charged ter-molecular complex arising from glycerol photoionisation, and natural transition orbitals for a Frenkel exciton state in a nine-unit model of a self-assembling nanotube.</p>1 aShao, Yihan1 aGan, Zhengting1 aEpifanovsky, Evgeny1 aGilbert, Andrew, T. B.1 aWormit, Michael1 aKussmann, Joerg1 aLange, Adrian, W.1 aBehn, Andrew1 aDeng, Jia1 aFeng, Xintian1 aGhosh, Debashree  uhttps://library.ncl.res.in/content/advances-molecular-quantum-chemistry-contained-q-chem-4-program-package