Hideo Fukutome

A molecular-orbital theoretical classification of reactions of singlet ground-state molecules

Abstract The reaction mechanisms of molecular systems in the ground singlet state are discriminated with the triplet stability—instability criterion of the restricted Hartree—Fock (RHF) solution for the entire system and with the phase continuity criterion of the highest occupied orbital involved. The criteria used are discussed in relation to the outcomes from the configuration-interaction approach.

Design of conjugated polymers with polaronic ferromagnetism

Abstract A new class of ferromagnetic conjugated polymers is proposed. These polymers have no built-in radicals, but spins are generated by doping. They have an alternating -A-B-A-B- structure. A is a block which gives a polaron on doping. B is a block which couples the A-block polaron spins. Possible ferromagnetism in polymers of this type is demonstrated using the PPP model.

Theory of Resonating Quantum Fluctuations in a Fermion System -- Resonating Hartree-Fock Approximation--

We develop a new general theory for large quantum fluctuations in a Fermion many·body system that cannot be described by fluctuations around the Hartree·Fock ground state but arises from resonance of different correlation structures. We start with an exact coherent state representation of a Fermion system on a unitary group. We show that the Hamiltonian in the coherent state representation has a close connection with the Hartree·Fock energy functional. From this, we can derive a new approximation called the resonating Hartree·Fock approximation in which a state is approximated by a superposition of non· orthogonal Slater deterrp.inants with different correlation structures. We derive the variation equations to determine a resonating Hartree· Fock wavefunction. We show that the resonance between degenerate broken symmetry Slater determinants may partially recover the symmetry. We discuss how to choose trial Slater determinants in a resonating Hartree· Fock wavefunction. We suggest that resonance of Slater determinants representing localized defects, such as solitons, polarons and breathers, produced in the long range order of the HF ground state may be the most important content of large quantum fluctuations in condensed matter systems.

Mechanisms of the reactions of singlet molecular oxygen with olefins

Abstract On the basis of the spin- and space-symmetry conservation criteria proposed previously, the cycloaddition reactions of singlet molecular oxygen toward olefins and the thermal decomposition of dioxelane are characterized with respect to the mechanistic feature (concerted, zwitterionic or biradical). The results are wholly compatible with observation.

PPP-UHF model of polyacetylene

Abstract A systematic analytical treatment and an overview of the Pariser-Parr-Pople (PPP) model in the unrestricted Hartree-Fock (UHF) approximation of trans-polyacetylene is described. The approximate analytical expressions of the regular density waves and soliton solutions of the UHF equation are derived. The predictions of the PPP-UHF model obtained previously using numerical computations are interpreted by means of these analytical results. The theoretical results and experiments are discussed and the importance of the Coulomb interaction in polyacetylene is shown.

Theory of the Unrestricted Hartree-Fock Equation and Its Solutions. I

Classification and characterization of the solutions of UHF equation are discussed on the. basis of a group theoretical consideration on their behavior for spin rotation and time reversal. It is shown that UHF solutions can be classified into eight classes with distinct behavior for spin rotation an:d time reversal. The properties of density matrix to characterize the eight classes are derived. From the properties, standard forms. of orbital for the eight classes are derived.

Orbital Optimization in the Resonating Hartree-Fock Approximation and Its Application to the One Dimensional Hubbard Model

A tractable direct optimization algorithm is developed to optimize orbitals in the Slater determinants (S-dets) in a resonating Hartree-Fock (Res HF) wave function. We reduce the variation space using the orbitals to put the first order energy variation in the steepest descent direction. The orbitals in the next iteration are determined so as to minimize the energy functional including up to the second order variation. This algorithm is applied to the one dimensional Hubbard model of half-filling. The optimized S-dets much deviate from the trial S-dets prepared from the HF calculations. The Res HF ground state generated with a few S-dets explains from 99.9 to 95.0% of the ground state correlation energy in all the correlation regimes. We have spin correlation functions with the correct short and long range behaviors and the lowest triplet and singlet spin excitations with correct dispersions, suggesting that the optimization of orbitals incorporates long range spin fluctuations and their mode-mode couplings.

Electronic and Lattice Structures of Isolated Se Chains and Defects in Them.II

Electronic and lattice structures of terminal and internal defects in a Se chain are systematically studied with the semi-empirical model developed previously. Structures of the defects are as follows: negative ion 1 C 1 - , a little altered helix; neutral radical 2 C 1 0 , and positive singlet ion 1 C 1 + , planer structures with four atoms; positive triplet ion 3 C 1 + , an acute triangle; n-type polaron 2 P - , locally relaxed helix; p-type polaron 2 P + and self-trapped triplet exciton 3 Ex, planer zig-zag structures with five atoms; intimate valence alternation pair (IVAP), a ramification of a Se atom. The IVAP is of C 3 + -C 1 - type. Interactions of a Se chain with Li, H and O are studied as a model of the effects of the wall on a Se chain enclosed in a mordenite channel (M-Se). A Se chain makes unusual charge transfer complexes with Li. Hydrogen binds to an internal Se making it C 3 + type or blocks a terminal Se. Based on these calculations we propose a model for photo-induced events in M-Se.

The Group Theoretical Structure of Fermion Many-Body Systems Arising from the Canonical Anticommutation Relation. I --Lie Algebras of Fermion Operators and Exact Generator Coordinate Representations of State Vectors--

We study in this series the group theoretical structure of Fermion many-body systems arising from the canonical anticommutation relation of the annihilation-creation operators. Owing to the canonical anticommutation relation, a Fermion system with N single particle states has at least six Lie algebras of Fermion operators, a U(N), an SO(2N), an SO(2N + I), an SO(2N +2) and two U(N + 1) Lie algebras. There are also two Clifford algebras of 2N and 2N + 1 dimensions. The Fermion space is shown to belong to the spinor representations of the SO(2N), SO(2N + 1) and SO(2N +2) groups. The canonical transformations generated by the U(N), SO(2N) and SO(2N + 1) Lie algebras are characterized as the transformations to induce the linear U( N), SO(2N) and SO(2N + 1) transformations for the Clifford algebras. The independent (quasi-) particle type wave functions of three kinds including the Hartree-Fock and Hartree-Bogoliubov wave functions are constructed by means of the canonical transformations and their relationship is studied. We derive three exact generator coordinate representations for state vectors in which the generator coordinates are the U(N), SO(2N) or SO(2N + 1) group and the generating functions are the independent (quasi-) particle type wave functions. We characterize the structures of state vectors in the generator coordinate representations and study the relationship of the three representations.

Inactivation of Escherichia coli ribosomes by ultraviolet irradiation: I. Activity of poly U-directed polyphenylalanine synthesis☆

Inactivation of ribosomes, isolated from Escherichia coli strains B and H, by irradiation with ultraviolet light of wavelength 253.7 mμ was studied as regards the poly U-directed polyphenylalanine synthesizing activity. The principal findings were as follow. (1) Ultraviolet inactivation of ribosomes of both strains obeys single-hit kinetics, but the rate of inactivation is apparently different for the ribosomes of the two strains. (2) Inactivation rates of the subunits are much smaller when irradiated in the 70 s complex than in the dissociated state. (3) A fraction of ultraviolet-irradiated subunits loses the ability to associate with the partner subunit. In the case of B strain ribosomes, another fraction of irradiated subunits retains the ability to associate but fails to interact properly with the partner; furthermore, an active subunit appears to select and associate preferentially with an active partner among a population containing such damaged subunits. (4) In the 30 s subunit, the target size of functional sites related to subunit interaction is much larger than that of functional sites unrelated to it. These results suggest that the interaction between the subunits is an intricate one and has a crucial role in the ribosomal function. (6) The number of critical RNA bases, estimated from the inactivation cross-section, is very much smaller than the total number of pyrimidine bases in the ribosomal RNA.