Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Integral hopping

Tlie suffices i and J refer to individual atoms and S and Sj to the species of the atoms involved. The summation over j extends over those neighbors of the atom i for which ry, the separation of atoms i and J, is within the cutoff radii of these potentials. The second term in Equation (la) is the attractive many-body term and both V and are empirically fitted pair potentials. A Justification for the square root form of the many-body function is provided in the framework of a second moment approximation of the density of states to the tight-binding theory incorporating local charge conservation in this framework the potentials represent squares of the hopping integrals (Ackland, et al. 1988). [Pg.357]

The UHF solution appears when the hopping integral t becomes small and leads to a spin density wave. The localization of the MOs leads to a and b atom centered orbitals, localized around odd and even labelled atoms respectively. [Pg.108]

Here U is the intra-atomic interaction defined in Chapter 4 and t, the hopping integral, is equal to B/2z, where B is the bandwidth and z is the coordination number. The suffixes i and j refer to the nearest-neighbour sites, and aia is the creation operator for site i. The suffix a refers to the spin direction. Hubbard found that a metal-insulator transition should occur when B/U = 1.15. Hubbard s analysis did not include long-range interactions, and therefore did not predict any discontinuity in the number of current carriers. [Pg.123]

For more detailed analysis, we introduce the effect of the hopping integral of 2p orbitals between neighboring oxygen ions. Let us consider the configuration of 2p orbitals on the oxygen ions labeled i vi in Fig. 5 where... [Pg.207]

For J0 0 and at zero temperature the hopping integral is roughly reduced... [Pg.319]

The values of the mixing coefficients cos and sin depend on the coupling strength, which we can define in terms of the resonance (hopping) integral H12 measured relative to the distance Hn-H22 between AO levels, giving157 ... [Pg.100]

For t2= 0 the Hamiltonian H describes a one-dimensional Hubbard lattice (chain) with the alternating values of hopping integrals. Evidently, the spectrum of such a system must coincide with the set of singular values [Pg.706]

As has been shown by Takahashi [38], the isotropic case of the triangular lattice with a positive value of hopping integrals has a dominantly ferromagnetic character. Therefore, increasing the value of t2 (f2 = t3) can lead to the changing of the ground state total spin of the lattice strip. [Pg.713]

Note, that the similar result may be found for the lattice formed by two segments with different hopping integrals t, and t respectively and a = 0. For... [Pg.721]


See other pages where Integral hopping is mentioned: [Pg.254]    [Pg.254]    [Pg.254]    [Pg.358]    [Pg.373]    [Pg.106]    [Pg.115]    [Pg.201]    [Pg.222]    [Pg.346]    [Pg.311]    [Pg.511]    [Pg.516]    [Pg.749]    [Pg.245]    [Pg.32]    [Pg.203]    [Pg.204]    [Pg.206]    [Pg.207]    [Pg.31]    [Pg.111]    [Pg.313]    [Pg.53]    [Pg.108]    [Pg.283]    [Pg.311]    [Pg.99]    [Pg.687]    [Pg.709]    [Pg.719]    [Pg.725]    [Pg.18]    [Pg.325]    [Pg.18]    [Pg.169]    [Pg.178]    [Pg.179]    [Pg.183]    [Pg.183]    [Pg.184]   
See also in sourсe #XX -- [ Pg.201 ]

See also in sourсe #XX -- [ Pg.67 ]




SEARCH



Hopping integral, band structure

Hops

© 2024 chempedia.info