Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.

A Green's function approach to analysing the effects of random synaptic background activity in a model neural network

Abstract: The effect of randomly distributed synaptic background activity on the states of self-sustained firing in a model neural network with shunting is investigated. Using mean field theory, the steady state of the network is expressed in terms of an ensemble-averaged single-neuron Green's function. This Green's function is shown to satisfy a matrix equation identical in form to that found in the tight-binding-alloy model of excitations on a one-dimensional disordered lattice. The ensemble averaging is then performed using a coherent potential approximation thus allowing the steady-state firing rate of the network to be determined. The firing rate is found to decrease as the mean level of background activity across the network is increased; a uniform background (zero variance) leads to a greater reduction than a randomly distributed one (non-zero variance).

Random-bethe-lattice model applied to the electronic structure of amorphous and liquid silicon

Abstract: Bethe lattices of arbitrary number of nearest-neighbor atoms and geometrical configurations are defined for the standard {ital sp}{sup 3}{ital s*} tight-binding Hamiltonian that gives correctly both valence and conduction bands of crystalline Si. Averaged densities of states are obtained through a well-grounded extension of the coherent-potential approximation to random Bethe lattices with off-diagonal disorder. In that way, a unified picture of the electronic structure of Si in amorphous and liquid phases is obtained. Formation energies of dangling and floating bonds are estimated within Chadi's tight-binding scheme.

Computational materials design of filled tetrahedral compound magnetic semiconductors

Abstract: Based on first-principles calculations within the density functional theory, materials design of filled tetrahedral compound magnetic semiconductors is proposed. By using the Korringa–Kohn–Rostoker coherent potential approximation, electronic structures of Mn-doped LiZnAs, LiZnP and LiZnN are calculated. First, by estimating free energy, phase diagrams of these systems are predicted. It is shown that these systems are phase separating systems and favor spinodal decomposition. However, by introducing Li vacancies, spinodal decomposition is strongly suppressed and Mn can be doped up to high concentration. Moreover, the introduced Li vacancies induce ferromagnetic interaction between Mn and thus we can expect high Curie temperature ( T C ) in these systems. To see the chemical trend, electronic structure and T C of Li(Zn, Cr)As are also calculated.

Dynamical Coherent-Potential Approximation and Tight-Binding Linear Muffintin Orbital Approach to Correlated Electron System

Abstract: Dynamical coherent-potential approximation (CPA) to correlated electrons has been extended to a system with realistic Hamiltonian which consists of the first-principles tight-binding linear muffintin orbital (LMTO) bands and intraatomic Coulomb interactions. Thermodynamic potential and self-consistent equations for Green function are obtained on the basis of the functional integral method and the harmonic approximation which neglects the mode–mode couplings between the dynamical potentials with different frequency. Numerical calculations have been performed for Fe and Ni within the second-order dynamical corrections to the static approximation. The band narrowing of the quasiparticle states and the 6 eV satellite are obtained for Ni at finite temperatures. The theory leads to the Curie–Weiss law for both Fe and Ni. Calculated effective Bohr magneton numbers are 3.0 µ B for Fe and 1.2 µ B for Ni, explaining the experimental data. But calculated Curie temperatures are 2020 K for Fe and 1260 K for Ni, being ...