Charge-transfer in time-dependent density-functional theory via spin-symmetry-breaking

Long-range charge-transfer excitations pose a major challenge for time-dependent density functional approximations. We show that spin-symmetry-breaking offers a simple solution for molecules composed of open-shell fragments, yielding accurate excitations at large separations when the acceptor effectively contains one active electron. Unrestricted exact-exchange and self-interaction-corrected functionals are performed on one-dimensional models and the real LiH molecule within the pseudopotential approximation to demonstrate our results.Comment: 5 pages, 4 figure

Acid/base-triggered switching of circularly polarized luminescence and electronic circular dichroism in organic and organometallic helicenes.

Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene-bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a. Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum-chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene-bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge-transfer-type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation

Tetraphenylpentalenide organolanthanide complexes

The D2h symmetrical 1,3,4,6-tetraphenylpentalenide is an excellent ligand for the stabilisation of strongly coloured bis(pentalenide) LnIII sandwich complexes. These easily accessible compounds complement previously reported lanthanide organometallics and provide new opportunities to understand the roles of the f-orbitals in electronic structure and bonding

A diuranium carbide cluster stabilized inside a C80 fullerene cage.

Unsupported non-bridged uranium-carbon double bonds have long been sought after in actinide chemistry as fundamental synthetic targets in the study of actinide-ligand multiple bonding. Here we report that, utilizing Ih(7)-C80 fullerenes as nanocontainers, a diuranium carbide cluster, U=C=U, has been encapsulated and stabilized in the form of UCU@Ih(7)-C80. This endohedral fullerene was prepared utilizing the Krätschmer-Huffman arc discharge method, and was then co-crystallized with nickel(II) octaethylporphyrin (NiII-OEP) to produce UCU@Ih(7)-C80·[NiII-OEP] as single crystals. X-ray diffraction analysis reveals a cage-stabilized, carbide-bridged, bent UCU cluster with unexpectedly short uranium-carbon distances (2.03 Å) indicative of covalent U=C double-bond character. The quantum-chemical results suggest that both U atoms in the UCU unit have formal oxidation state of +5. The structural features of UCU@Ih(7)-C80 and the covalent nature of the U(f1)=C double bonds were further affirmed through various spectroscopic and theoretical analyses

Acid/base-triggered switching of circularly polarized luminescence and electronic circular dichroism in organic and organometallic helicenes

Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene-bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a. Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum-chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene-bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge-transfer-type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation

Проектирование системы электроснабжения цементного завода

Цель работы: разработка системы электроснабжения промышленного предприятия. В процессе исследования произведен выбор метода расчета, осуществлён расчет электрических нагрузок завода и рассматриваемого цеха, произведён выбор оборудования и его проверка при различных режимах работы. В результате исследования была спроектирована модель электроснабжения промышленного предприятия, представлена ее техническая целесообразность и безопасность для окружающей среды. Основные конструктивные, технологические и технико-эксплуатационные характеристики: исследуемый завод состоит из двадцати цехов, из них шесть цехов относятся ко второй категории по надежности электроснабжения; напряжение питающей линии 110 кВ; рабочие напряжения внутри завода: 10/0,4 кВ; схема электроснабжения цеха - магистральная.Objective: Development of power supply system of the industrial enterprise. In the research process there was chosen the method of calculation, calculation of electrical loads of the enterprise, selection of equipment and it's verification under various operationg conditions. In the result of the research the model of electrical supply system has been designed. Also there are economical effectiveness and environmental security. Basic constructive, technological and operational characteristics: there are twenty departments, six of them belong to the second power supply reliability category; voltage of the feeding line is the 110 kV; operating voltages within the plant: 6, 0.4 kV; power supply of consumers of mechanical-repair shop is carried out by trunk power supply network

Time dependent density functional theory calculation of van der Waals coefficient C6_{6} of alkali-metal atoms Li, Na, K, alkali dimers Li2_{2}, Na2_{2}, K2_{2} and sodium clusters Nan_{n}

In this paper we employ all-electron time dependent density functional theory (TDDFT) to calculate the long range dipole-dipole dispersion coefficient (van der Waals coefficient) $C_{6}$ of alkali-metal atoms Li, Na, K, alkali-metal atom dimers Li$_{2}$, Na$_{2}$, K$_{2}$ and sodium clusters containing even number of atoms ranging from 2 to 20 atoms. The dispersion coefficients are obtained via Casimir-Polder expression which relates it to the frequency dependent linear polarizabilty at imaginary frequencies. The frequency dependent polarizabilities are calculated by employing TDDFT--based complete sum-over-states expressions for the atoms, and direct TDDFT linear response theory for the closed shell dimers and clusters.Comment: 14 pages of text and 4 figure