نتایج جستجو برای: valence bond theory
تعداد نتایج: 859522 فیلتر نتایج به سال:
We study the quantum dimer model on the triangular lattice, which is expected to describe the singlet dynamics of frustrated Heisenberg models in phases where valence bond configurations dominate their physics. We find, in contrast to the square lattice, that there is a truly short ranged resonating valence bond phase with no gapless excitations and with deconfined, gapped, spinons for a finite...
The nodal structures of atomic wave functions based on a product of spatial orbitals, namely, restricted, unrestricted, and generalized valence bond wave functions, are shown to be equivalent. This result is verified by fixed node-diffusion Monte Carlo simulations for atoms up to Ne. Also for a molecular system, Li(2) at the equilibrium geometry, a multideterminantal generalized valence bond wa...
A new method for the accurate a priori calculation of atomic and molecular energies is proposed. The new method agrees with experiment to within less than 1 kcal/mole in all cases examined thus far, and is applicable to excited states and to transition states for chemical reactions. Since the new method corrects the results of generalized valence bond calculations for the effects of electron pa...
A mixed Valence-Bond/Hartree-Fock method applied to all valence electrons calculations on finite size clusters was derived in order to size up the relative magnitude of the coulombic interactions between conduction electrons in organic conductors. An effective
Carboxylic acids are hydrocarbon derivatives containing a carboxyl (COOH) moiety. Recall that carbon has four valence electrons and therefore requires four electrons or bonds to complete its octet. Based on this valence and bonding order, carbon forms four bonds in its neutral state, and these may be four single bonds or combinations of single and multiple bonds. Oxygen has six valence electron...
Recent high-resolution soft X–ray resonant inelastic X-ray scattering technique enables us to distinguish valence electronic structure of water molecules having different hydrogen-bond configurations in the liquid phase. Moreover, in the elastic region, well-separated multiple vibrational structures appear, which corresponds to the internal OH stretch vibration in the ground state. Both the val...
We introduce the atomic valence active space (AVAS), a simple and well-defined automated technique for constructing active orbital spaces for use in multiconfiguration and multireference (MR) electronic structure calculations. Concretely, the technique constructs active molecular orbitals capable of describing all relevant electronic configurations emerging from a targeted set of atomic valence...
When an electronic system has strong correlations and a large spin-orbit interaction, it often exhibits a plethora of mutually competing quantum phases. How a particular quantum ground state is selected out of several possibilities is a very interesting question. However, equally fascinating is how such a quantum entangled state breaks up due to perturbation. This important question has relevan...
The crystal structure of sodium dipotassium citrate, Na(+)·2K(+)·C6H5O7 (3-), has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The Na(+) and one of the K(+) cations are six-coordinate, with bond-valence sums of 1.13 and 0.92 valence units, respectively, while another crystallographically independent K(+) cation is sev...
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