Abstracts of Congress
and Plenary Lectures

33

2CL

Interplay Between Experiment and Theory
Yuan-Tseh Lee
Academia Sinica, Taiwan
During the past 100 years, our understanding of chemistry has changed quite
substantially. First, the laws of thermodynamics allowed us to elucidate, chemical
equilibrium and chemical properties based on fundamental laws of nature. Then, theadvances made early in the twentieth century in the understanding of the laws of
mechanics governing the motion of microscopic particles, enabled us to explore
molecular structures and chemical changes, solely based on quantum mechanics.
However, because of the complexity of chemical system we are dealing with, neither
theoretical investigation nor experimental pursuit alone have been shown to be adequate
in advancing the basic understanding of chemistry. During the past fifty years, with theadvancement of sophisticated experimental methods and high speed electronic
computation, the interplay between experiment and theory has become more importantand more fruitful.
In this lecture, my personal perspective as well as some examples will be given toillustrate the interplay between experiment and theory during the last forty years,
especially in the field related to chemical dynamics. Some discussion will also be madeon the important challenges human society is facing today for our survival on thesurface of the earth.

34

2PL

Theoretical Studies of Chemical Reactions – Gas Phase Reactions
to Nano Structures, Catalyses, and Enzymatic Reactions in Groundand Excited Electronic States
Keiji Morokuma
Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japanand Cherry L. Emerson Center for Scientific Computation and Department of Chemistry,
Emory University, Atlanta, GA 30322, U.S.A.
The chemical reaction which creates, destroys, reorganizes chemical bonds to
produce new compounds is the most important subject of chemistry. I have beenabsorbed by this exciting world of chemical reactions from the beginning of my careerfor more than fifty years, since a hand-powered calculator was used to solve Hückel
secular equations for frontier electron densities of simple aromatic hydrocarbons.
Theoretical/computational studies have come a long way and are now playing thecentral role in understanding the mechanism and dynamics of chemical reactions and in
helping designing more useful chemical reactions and catalysts. The theory can study
not only the reaction of the ground state of molecules in gas phase but also reactions of
excited electronic states as well complicated reactions of complex molecular systems.
The information theoretical/computational studies can provide is often complementary
to the information experimental studies provide, and research on chemical reactions is
becoming impossible without strong collaboration between theorists andexperimentalists.
I will discuss a few examples of recent theoretical/computational studies performedin my group on chemical reactions. The areas to be covered include A. efficient andautomatic determination of reaction pathways; B. self-assembly reactions of small
carbon clusters to form fullerenes and carbon nanotubes with or without transition metal
catalysts; C. homogeneous catalyses in solution and in the confined space created byprotein, D. reactions of metalloenzymes with active site models and in protein
environment, and E. chemical and biochemical processes involving excited electronic
states.

35

4PL-1
Understanding Nucleation Phenomena at Large Metastability: From Gas-Liquid
Transition to Metastable Solids and Polymers
M. Santra, R. S. Singh, S. Chakrabarty and B. Bagchi*
Solid State and Structural Chemistry Unit,
Indian Institute of Science, Bangalore – 560 012.
(http://www.liquid.sscu.iisc.ernet.in)*Email: bbagchi@sscu.iisc.ernet.in

Abstract
We have revisited the apparently well-studied problem of nucleation and growth of astable phase inside a parent metastable phase, particularly near the spinodal curve. We
have undertaken extensive computer simulation studies to probe the molecularmechanism for the onset of instability in a wide range of systems (both for 2 and 3
dimensional Lennard-Jones fluid and nearest neighbour Ising model). We haveconstructed the multidimensional free energy surface of nucleation as a function ofmultiple reaction coordinates [1]. While the classical Becker-Döring (BD) picture ofhomogenous nucleation, that assumes the growth of a nucleus by single particle
addition, holds good at low to moderate supersaturation, the formation of the newstable phase becomes more collective and spread over the whole system at large
supersaturation. As the spinodal curve is approached from the coexistence line, thenucleation free energy barrier, as a function of the size of the largest liquid-likecluster, disappears at a supersaturation (well below the thermodynamic spinodal limit)that we term as kinetic spinodal [2]. Very close to the kinetic spinodal the free energy
surface becomes quite flat and the critical nucleus grows by diffusion on a barrierlesssurface. We have developed an alternative formalism to treat nucleation at large
supersaturation by introducing an extended set of order parameters in terms of the kth
largest liquid-like clusters, where k = 1 is the largest cluster in the system, k = 2 is thesecond largest cluster and so on [2]. We shall also discuss nucleation of metastable
solids and collapsed state of polymers.

References:
1. P. Bhimalapuram, S. Chakrabarty and B. Bagchi, Phys. Rev. Lett. 98, 206104(2007); S. Chakrabarty, M. Santra and B. Bagchi, Phys. Rev. Lett. 101,
019602 (2008); M. Santra, S. Chakrabarty and B. Bagchi. J. Chem. Phys. 129,
234704 (2008).
2. M. Santra, Rakesh S. Singh and B. Bagchi, J. Stat. Mech. P03017 (2011); M.
Santra and B. Bagchi, Phys. Rev. E, 83, 031602 (2011).

36

4PL-2
Short-time frictional solvent effects on conical intersection dynamics for a model
photoisomerizationabJoao Pedro Malhado , Riccardo Spezia and James T. Hynes

a,ca CNRS UMR 8640, Departément de Chimie, Ecole Normale Supérieure, 24 rue Lhomond, 75231, Paris, FRb CNRS UMR 8587, LAMBE, Université d’Evry, Bd. F. Mitterrand, 91025 Evry, FRc Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA

It is now well appreciated that conical intersections (CIs) often provide an efficient, ultrafast nonadiabatic transitionroute from an excited electronic state to the ground state for photochemical reactions [1]. Accordingly, much effort--both theoretical and experimental---has been devoted to their study. Our previous efforts in this area [2,3,4] havefocused on constructing an approximate model description aimed at elucidating and describing the influence of asolvent (and ultimately a more complex protein environment) on CI structure and dynamics in a photoreaction
context. Of particular interest to us are photoreactions in which significant intramolecular charge transfer in thechromophore results in strong coupling to a polar environment. The template for our efforts has been a two valencebond, three coordinate description of the cis-trans photoisomerization of a model protonated Schiff base (PSB), itself
a model for retinal, of interest in connection with vision. In this talk---after a brief review of salient features of thebasic model and prior relevant results such as minimum energy paths and inertial, non-dissipative trajectory results--we will describe our most recent results [5] addressing the inclusion in the model of short-time ‘friction’, describing
energy and momentum transfer effects on the CI and photoisomerization dynamics. These effects are modeled via a
generalized Langevin description of dynamical frictions on the PSB intramolecular twist and bond length alteration
coordinates and on a nonequilibrium dielectric continuum solvent coordinate. Two model solvents are examined,acetonitrile and water, which are characterized by different solvent time-scales. Nonadiabatic trajectories weregenerated via Tully’s molecular dynamics with quantum transitions, fewest switches algorithm [6]. The important
influence of the solvent-dependent generalized friction on the path to the solvent coordinate-induced seam of CIs
from the Franck-Condon excitation region, on the location of the nonadiabatic transitions to the ground electronic
state, and on the trans or cis ground state product distribution will be described.
[1] See e.g. B.G. Levine and T. J. Martinez, Ann. Rev. Phys. Chem., 58, 613 (2007).
[2] I. Burghardt, L.S. Cederbaum and J.T. Hynes, Faraday Discuss., 127, 395 (2004). For earlier efforts on CI ground state
reaction effects, see D.Laage, I. Burghardt, T.Sommerfeld and J. T. Hynes, J. Phys. Chem. A, 107, 11271 (2003).
[3] R. Spezia, I. Burghardt and J.T. Hynes, J. Molec. Phys.(Robb Issue), 104, 903 (2006).
[4] I.Burghardt and J.T. Hynes, J. Phys. Chem. A, 110, 11411 (2006).
[5] J. Malhado, Thesis, ENS (2009); J. Malhado, R. Spezia and J.T. Hynes, J. Phys. Chem. A, in press, 2010. DOI:
10.1021/jp106096m[6] J. C. Tully, J. Chem. Phys., 93, 1061 (1990).

37

4PL-3

A Computational Approach to the Study of Free Radical Chemistry
Leo Radom
School of Chemistry and Centre of Excellence for Free Radical Chemistry andBiotechnology, University of Sydney, Sydney, NSW 2006, Australia
Radicals are ubiquitous in chemistry and biology. Because they are reactive species,
they are often difficult to study experimentally and therefore theory has a potentially
useful role to play in their characterization. However, there are also challenges fortheory, particularly in the form of so-called spin contamination. In recent years, wehave been involved in formulating theoretical procedures that provide an improved
description for radicals. We have also been using such procedures to investigate thestructures, stabilities and reactivities of radicals. Highlights from this research will bepresented.

38

5PL-1
Quantum Chemistry in Schrödinger Accuracy
Hiroshi Nakatsuji
Quantum Chemistry Research Institute (QCRI) and JST CREST
Kyoto, Japan (h.nakatsuji@qcri.or.jp)
Quantum principles represented by the Schrödinger equation and Dirac-Coulomb equation havevast and strong quantitative predictive powers. However, this was not realized for over 80 years,
because we did not have a general method of solving these equations in high accuracy. However,recently, this author has found such method [1-3] and one major subject of our QCRI has been todevelop efficient methodology. To make theoretical quantum science to be truly predictive, we haveto establish accurate and useful method of solving these equations for our common molecularsystems.
The accuracy and reliability of our methodology were well established for rather small atoms andmolecules. For few-electron systems, like helium, we could give numerical proof on how accurate is
our methodology, not only for ground state [4] but also for excited states [5], and not only for energy,
but also for wave function itself, like local energy, cusp, and other properties [6]. This was so not
only for non-relativistic Schrödinger case, but also for relativistic Dirac-Coulomb case [7]. It was
further extended to non-BO case [8]. Though this was done mostly using variation principle where
we have to calculate analytical integrals, we have also proposed LSE (local Schrödinger equation)
method [9] which is integration-free method and completely general for any analytical functions thatare generated automatically by the Hamiltonian of the system (free complement methodology).
Further, we have introduced useful local sampling method, anti-symmerization method, andfrom-atom-to- molecule idea. These methods certainly contributed to increase the atomic andmolecular size to which our theory is applicable.
Here, we will introduce some new ideas and formulations on this line of research and show somecomputational results.
References[1] Nakatsuji, JCP 113, 2949 (2000); Nakatsuji, Davidson, JCP 115, 2000 (2001).
[2] Nakatsuji, Ehara, JCP 117, 9, (2002); 122, 194108 (2005)[3] Nakatsuji, PRL 93, 030403 (2004), PRA, 72, 062110 (2005)[4] Kurokawa, Nakashima, Nakatsuji, PRA, 72, 062502 (2005); Nakashima, Nakatsuji, JCP, 127,
224104 (2007); 128, 154107 (2008); Kurokawa, Nakashima, Nakatsuji, PCCP, 10, 1 (2008);
Nakatsuji, Nakashima, Adv. Theor. Atom. Mol. Systems, B 47 (2009)[5] Nakashima, Hijikata, Nakatsuji, JCP, 128, 154108 (2008).
[6] Nakashima, Nakatsuji, PRL, 101, 240406 (2008); Nakatsuji, Nakashima, IJQC, 109, 2248
(2009); Bande, Nakashima, Nakatsuji, Chem. Phys. Lett., 496, 347 (2010).
[7] Nakatsuji, Nakashima, PRL, 95, 050407 (2005). Ishikawa, Nakashima, Nakatsuji, JCP, 128,
124103 (2008)[8] Hijikata, Nakashima, Nakatsuji, JCP, 130, 024102 (2009).
[9] Nakatsuji, Nakashima, Kurokawa, Ishikawa, PRL, 99, 240402 (2007)39

6PL-1

Looking at the world from a coupled-cluster perspective
Rodney J. Bartlett,1 S. Ajith Perera,1 M. Musial,1 P. Verma,1 M. Strassberg1
1
Quantum Theory Project, Departments of Chemistry and Physics, University of Florida,USA
In this talk we will address the broader context of coupled-cluster (CC) theory inchemistry. The theory offers an approach to a new correlated orbital theory (COT) thathas similar computational demands to density functional theory (DFT) but is built upon
the premise that the one-particle spectrum of a molecule, its principal ionization
potentials and electron affinities should be right. Approximations to these equations canbe made to provide the computational advantages of an effective one-particle theory.
A related topic is the role of the random phase approximation (RPA) in defining acorrelation potential for DFT. We introduce the concept of ‘coulomb attenuation” as away to better treat the correlation problem, by first solving for Coulomb-onlyinteractions, leaving the exchange and subsequent correlation to simpler, perturbative
treatments. This new division of the correlation problem depends upon the close
correspondence between CC theory and its RPA approximation limited to the sum ofring diagrams.

40

6PL-2Developments of Broken Symmetry Methods
Application to the CaMn4O5 Cluster at OEC of PSII Refined to 1.9 Å
X-Ray Resolution
K. Kanda,1 S. Yamanaka, 1 T. Saito, 1 Y. Umena, 2 K. Kawakami, 3 J. R. Shen, 2
N. Kamiya, 3 M. Okumura, 1 H. Nakamura, 4 Y. Yoshioka, 5 K. Yamaguchi,1,6
1Graduate School of Science, Osaka University, Toyonaka, 560-0043, Japan
2
Graduate School of Natural Science and Technology, Okayama University, 700-8530
3Graduate School of Science, Osaka City University, Sugimoto, 558-8585, Japan
4
Protein Institute, Osaka University, Suita, 560-0871, Japan
5
Graduate School of Engineering, Mie University, Tsu, 514-8507, Japan
6
TOYOTA Physical & Chemical Research Institute, Aichi, 480-1192, Japan
In this lecture historical developments of broken symmetry methods at Osaka [1-4]have been briefly reviewed, particularly, in relation to electronic and spin structures oforganic polydiradicals and transition-metal oxides with local spins. Past decades,
manganese-oxo (Mn=O) and related manganese-oxides species [3,4] have been received
great interest concerning with water splitting reaction at oxygen evolving complex(OEC) of photosynthesis II (PSII). Here, we present our recent BS UB3LYP
computational results [5] on the CaMn4O5 cluster of PSII refined to 1.9 Å X-ray
resolution [6] reported by Shen and Kamiya and their collaborators.
Possible electronic and spin structures of the CaMn4O5 cluster have been
investigated by UB3LYP assuming the X-ray structure [6]. All the BS configurations
feasible for the valence configurations of the cluster, Mn(III)xMn(IV)y (x,y = 0-4), havebeen constructed by the HOMO-LUMO mixing and other techniques. The spin andcharge populations obtained by UB3LYP are consistent with BS configurations
available. The effective exchange interactions (J) between manganese ions in the cluster
are determined by our computational procedures based on the approximate projection(AP). Full geometry optimizations of the antiferromagnetic exchange-coupled statesof the cluster have been performed for comparison with the X-ray result [4]. The natureof chemical bonds of the cluster is also investigated by the natural orbital analysis of the
BS solutions to elucidate possible mechanisms of water splitting reaction. Implicationsof the present computational results are also discussed briefly.
[1] K. Yamaguchi, T. Fueno and H. Fukutome, Chem. Phys. Lett. 22, 461 (1973).
[2] K. Yamaguchi, Chem. Phys. Lett. 33, 330 (1975); 35, 230 (1975); 66, 395 (1979).
[3] K. Yamaguchi, Y. Takahara and T. Fueno, Appl. Quant. Chem, p155-p184 (1986).
[4] K. Yamaguchi et al, in Organic Peroxides (W. Ando Ed., Wiley, 1992) p1-p100.
[5] K. Kanda et al, Chem. Phys. Lett. 506, 98 (2011)[6] Y. Umena, K. Kawakami, J. R. Shen, N. Kamiya, Nature 473, 55 (2011).

41

6PL-3Rate of convergence of basis expansions in quantum chemistry
Werner Kutzelnigg,1
1
Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Germany
Traditional expansions in an orthonormal basis of the type of a Fourier series
are very sensitive to the singularities of the function to be expanded. Exponential
convergence is only possible, if the basis functions describe the singularities of the
expanded functions correctly. Otherwise only an inverse-power-law convergence isrealized, which is usually slow. Example: the slow convergence of the CI expansion
due to the correlation cusp. An improved convergence, though still of inverse-power
type, can be achieved, if one augments the basis by functions that describe thesingularities of the wave function correctly, like in the R12 method.
Alternative: a discretized integral transformation, as in the conventional expansion of wave functions in a Gaussian basis. Such expansions are surprisingly insensitive to singularities of the wave function to be expanded (e.g. the nuclear cusp).
√
The rate of convergence is of a new type, with an error estimate ∼ exp(−a n),
if n is the basis size. For the expansion of the hydrogenic ground state function
in an even-tempered Gaussian basis, simple closed expressions for the asymptotic
error can be derived. This can be generalized to the relativistic case, where the convergence is qualitatively similar to the non-relativistic one, in spite of the stronger
singularity in the relativistic wave function.
References:
W. K, Int J. Quantum Chem. 51, 447 (1994);
Computational Quantum Chemistry: a Primer, by E. Cances, M. Defrancheschi,
W. Kutzelnigg, C. Le Bris, Y. Maday , Handbook of Numerical Analysis,Vol. X,
Elsevier 2003
W.K. J. Chem. Phys. 126, 201103 (2007) .
W.K. AIP conference proceedings, in press 2011
E-mail: werner.kutzelnigg@rub.de42

6PL-4

Analysis and Control of Electronic Motion in the Time Domain
E.K.U. Gross
Max Planck Institut für Mikrostrukturphysik, Weinberg 2, 06108 Halle, Germany
This lecture is about how electronic motion can be monitored, analyzed and,ultimately, controlled, in real time. In particular:(i) A novel approach to describe electronic transport through single
molecules or atomic wires, sandwiched between semi-infinite leads, will bepresented. The basic idea is to propagate the time-dependent Kohn Shamequations in time upon ramping up a bias between the metallic leads. In thisway, genuinely time-dependent phenomena, not accessible in the standard
Landauer approach, can be addressed. For example, employing an Andersonmodel, we demonstrate that Coulomb blockade corresponds, in the timedomain, to a periodic charging and discharging of the quantum dot [1].
(ii) With modern pulse-shaping facilities, the control of electronic motion is
becoming more and more realistic. By combining quantum optimal control
theory with TDDFT, we calculate shaped laser pulses suitable to control, e.g.,
the chirality of currents in quantum rings [2], the location of electrons in double
quantum dots, as well as the enhancement of a single peak in the harmonic
spectrum of atoms and molecules.
(iii) In all practical TDDFT calculations, approximate forms of the exchangecorrelation potential need to be employed. One of the most popular
approximations, the adiabatic local-density approximation (ALDA) will beanalyzed as to whether the main error comes from the adiabaticity assumption,i.e. locality in time, or from the LDA, i.e. locality in space. For an exactly
solvable model where the exact adiabatic approximation can be extracted,
we find the surprising fact, that the adiabaticity assumption can be an excellent
approximation even in highly intense laser fields [3].
(iv) Finally, the coupling between electronic and nuclear motion will be
addressed. As a first step towards a full ab-initio treatment of the coupledelectron-nuclear motion in time-dependent external fields, we deduce an exact
factorization of the complete wavefunction into a purely nuclear part and amany-electron wavefunction which parametrically depends on the nuclear
configuration. We derive formally exact equations of motion for the nuclear andelectronic wavefunctions [4]. These exact equations lead to a rigorous definitionof time-dependent potential energy surfaces as well as time-dependent
geometric phases. With the simple example of the hydrogen molecular ion in alaser field we demonstrate the significance of these concepts in understanding
the full electron-ion dynamics. In particular, the time-dependent potential energy
surfaces are shown to represent a powerful tool to analyse and interpret
different (direct vs. tunneling) types of dissociation processes.
[1] S. Kurth, G. Stefanucci, E. Khosravi, C. Verdozzi, E.K.U. Gross, Phys. Rev.Lett.104,
236801 (2010).
[2] E. Räsänen, A. Castro, J. Werschnik, A. Rubio, E.K.U. Gross, Phys. Rev. Lett.
98,157404 (2007).
[3] M. Thiele, E.K.U. Gross and S. Kümmel, Phys. Rev. Lett. 100, 153004 (2008).
[4] A. Abedi, N.T. Maitra, E.K.U. Gross, Phys. Rev. Lett. 105, 123002 (2010).
43

7PL-1Treatment of Vibronic Properties in Infinite Periodic Systems
Bernard Kirtman1, Matteo Ferrabone2, Valentina Lacivita2, Michel Rèrat3,
Roberto Orlando4, and Roberto Dovesi2
1

Department of Chemistry and Biochemistry, University of California,
Santa Barbara, USA
2
Departimento di Chimica IFM, Universitá di Torino, Italy3
Equipe de Chimie Physique, Universitè de Pau et des Pays de l’Adour, France
4
Dipartimento de Scienze e Technologie Avanzate,
Universitá del Piemonte Orientale, Italy
There are many important spectroscopic properties that are determined either entirely,or in large part, by the electronic response to nuclear displacements. Some examples
are Raman intensities, static and dynamic (i.e. nonlinear optical) vibrational
hyperpolarizabilities, and vibrational circular dichroism. The practical calculation ofvibronic properties for infinite periodic systems, or systems that may be modeled as
infinite and periodic, typically requires special considerations. We will focus here
primarily on static and dynamic vibrational hyperpolarizabilities that have recently
been obtained, for the first time, by the finite field nuclear relaxation (FF-NR)
method. The successful implementation of this computational scheme in the
CRYSTAL computer code, which utilizes Gaussian-type basis sets, will be described.
B3LYP results, in particular for BN nanotubes, indicate that vibrational contributions
can be as important, or much more important, than pure electronic contributions
depending on the property, tensor component, optical frequency, and nanotube radius.
Application of the FF-NR treatment, as well as extensions of this approach, to othersystems will be discussed along with computational methods for other properties.

44

7PL-2Singlet Fission
Josef Michl1,2 and ZdenČk Havlas1
1
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech
Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic2
Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO
80309-0215, USA
Singlet fission is a little known and usually inefficient form of multiple exciton
generation from a single photon. It is a spin-allowed process in which a chromophore
excited into its singlet state shares energy with a nearby ground state chromophore,
producing a pair of triplet excited chromophores coupled into an overall singlet. Singlet
fission has been observed in a very small number of aromatic hydrocarbons, particularly
tetracene and pentacene, and also in a few conjugated polymers and carotenoids, starting
half a century ago. It had received little attention until very recently, when it was pointed
out that if it were fully efficient, and if it were possible to achieve charge separation fromboth resulting triplets, the limiting theoretical efficiency of a simple photovoltaic cellwould be increased from 1/3 to nearly 1/2. In order to explore the potential of thephenomenon in solar cells, a much wider selection of structures for which singlet fission
is efficient is needed.
We shall describe a first-principles approach to the problem of designing molecular
structures for which singlet fission is efficient. This involves developing three sets ofstructural design rules: (i) for finding chromophores in which the conditions E(S1)  2
E(T1) and E(T2)  2 E(T1) are satisfied, making singlet fission exoergic and triplet
annihilation endoergic, (ii) for finding chromophore coupling that maximizes the rate ofsinglet fission relative to all other possible decay processes in a dimer, oligomer, or
crystal, and (iii) for finding arrangements that maximize the likelihood of two
independent charge separation events from a triplet pair in competition with all otherdecay modes. The first application of the rules produced a material that exhibited a2005 triplet yield.

45

7PL-3

State-specific Multi-reference Coupled Cluster Formalisms:
An Overview of a Suite of Recent Developments
Debashis Mukherjee
Raman Center for Atomic, Molecular and Optical Sciences
Indian Association for the Cultivation of Science
Jadavpur, Kolkata 700 032, India
In this talk, I will present an overview of some of the recent developments in State-specific Multireference (SS-MR) many-body formalisms. The overarching theoretical framework is the use of the
Jeziorski-Monkhorst (JM) cluster ansatz for the state-specific (SS) wave operator acting on a linear
combination of model functions spanning a complete active space (CAS). The JM ansatz, when used in
the context of the SS formalism, induces the “redundancy problem” of the number of cluster
amplitudes which exceeds the number of combining coefficients of the virtual functions present in thetarget state. By imposing two desirable features, from the formalism, viz. the avoidance of intruders
and the maintenance of size-extensivity, essentially unique sufficiency conditions resolving theredundancy can be found. I will give a survey of not only the parent formalism (the State-specific
MRCC) but also will discuss an approximant where an Internally Contracted treatment of the Inactive(ICI) is done to reduce the number of the most numerous amplitudes. Numerical performance of thevarious methods will be illustrated by example applications to challenging prototypical systems, withpronounced and varied multi-reference character. In particular, I will highlight the following insights
gained from the applications (1) the parent SS-MRCC theory in the usual CCSD truncation undermines
the importance of coupling of virtual functions which are doubly excited with respect to another,
thereby posing both slowness of convergence of the solutions and of somewhat poor performance; (2)an extended hierarchy of truncation schemes, viz. the SS-MRCCSDt/CCSDtq, with the t/q having thesame meaning as in the Adamowicz SR-MR Ansatz allows the leading missing virtual couplings and it
performs very well; (3) the SS-MRCCSD scheme, with localized orbitals obtained from individualtransformations on the core, active and virtual orbitals, performs spectacularly well, presumably
because the vastly reduced importance of the doubles-quadruples virtual couplings; (4) the ICIDMRCCSD, with the internally contracted treatment of the inactive double excitations perform nearly aswell as the parent SS-MRCCSD. The finding (3)indicates the potential importance of the SS-

MRCCSD method to treat large systems in a ‘local correlation’ framework. The finding (4) implies thatessentially the same accuracy as the parent theory can be attained if the inactive doubles are treated in acontracted manner.

46

8PL-1The K Supercomputer and Recent Advances in LC-DFT
Kimihiko Hirao
Advanced Institute for Computational Science, RIKEN, Kobe, Japan
Twice a year, the world’s supercomputers are ranked according to their level of
performance in a listing called the TOP500. On June 20, 2011, the K computer jointly
developed by RIKEN and Fujitsu was pronounced the fastest computer in the world in
the TOP500 listing announced at the 2011 International Supercomputing Conference in
Hamburg. The K computer came out way ahead of its competitors with a LINPACK
benchmark performance of 8.162 petaflops. The K computer’s achievement waswonderful news following as it did the devastation of the March 11 Great East Japan
Earthquake, and reinforces Japan’s strengths in science, technology and manufacturing.
It is my fervent hope that the international recognition given to the K computer will help
to prime Japan’s recovery from the disaster. It should be noted, however, the real test of
the K computer will be the results that are achieved through its use. With the
emergence of petascale computing platforms we are entering a new era of modeling.
Petascale computing will enable us to simulate physical processes on a scale never seen
before, and approach convergence for dynamical processes never thought possible.
The K computer will open up a new frontier in computational chemistry.
DFT has emerged as a powerful computational tool for the chemical systems. It issimple and conceptual. KS-DFT calculation takes about the same amount of time as a
HF calculation, yet unlike HF, we get a correlated result from KS-DFT. Many of the
problems of KS-DFT have mostly been a consequence of not having accurate
functionals and potentials. Recently there has been considerable interest in thelong-range correction (LC) DFT. In the LC scheme the exchange functional ispartitioned with respect to the inter-electronic separation into long-range andshort-range parts using a standard error function. The LC solves many of the problemsof the conventional KS-DFT. Recently it was demonstrated that the LC satisfies
Koopmans’theorem, which implies that the eigenvalues and eigenvectors connected to
the Kohn-Sham equation have a strict physical meaning. Different from Hartree-Fock
Koopmans ionization energy, DFT Koopmans ionization energy to some extent takes
into account the relaxation and correlation effects. Recent advances in LC-DFT will be
discussed.

47