Conventional density functional theory DFT fails for materials with strongly correlated electrons, such as late transition metal oxides. Large errors in the intra-atomic Coulomb and exchange interactions are the source of this failure. The DFT+U method has provided a means, through empirical parameters, to correct these errors. Here, we present a systematic ab initio approach in evaluating the ...

Projection-based embedding provides a simple and numerically robust framework for multiscale wavefunction-in-density-functional-theory (WF-in-DFT) calculations. The approach works well when the approximate DFT is sufficiently accurate to describe the energetics of the low-level subsystem and the coupling between subsystems. It is also necessary that the low-level DFT produces a qualitatively re...

The Empirical Tight Binding (ETB) method is widely used in atomistic device simulations. The reliability of such simulations depends very strongly on the choice of basis sets and the ETB parameters. The traditional way of obtaining the ETB parameters is by fitting to experiment data, or critical theoretical bandedges and symmetries rather than a foundational mapping. A further shortcoming of tr...

Orbital-free (OF) methods promise significant speed-up of computations based on density functional theory (DFT). In this field, the development of accurate kinetic-energy density functionals remains an open question. In this chapter we review the shell-correction method (SCM, commonly known as Strutinsky’s averaging method) applied originally in nuclear physics and its more recent formulation i...

AIMS To investigate the correlation between body weight and defibrillation threshold (DFT) for transvenous lead systems using a porcine model. METHODS AND RESULTS Twenty-eight pigs were anaesthetised and DFTs assessed in single and dual coil configurations using a four-reversal binary search method. DFT was correlated with body weight in the RV --> Can and RV --> SVC + Can configurations. A P...

New algorithms for computing the Discrete Fourier Transform (DFT) spectra along different directions are derived and implemented. For computing the DFT spectrum along any given direction (containing N DFT frequencies), a new algorithm is presented that requires N ( N 1 ) additions and a single 1-D FFT. As expected, for a single direction, the directional FFT algorithm is significantly faster th...

Recently, we introduced a new density-functional theory ~DFT! approach for the calculation of NMR shielding constants. First, a hybrid DFT calculation ~using 5% exact exchange! is performed on the molecule to determine Kohn–Sham orbitals and their energies; second, the constants are determined as in nonhybrid DFT theory, that is, the paramagnetic contribution to the constants is calculated from...

This paper presents a new fast Discrete Fourier Transform (DFT) algorithm. By rewriting the DFT, a new algorithm is obtained that uses 2 n?2 (3n?13)+4n?2 real multiplications and 2 n?2 (7n? 29) + 6n + 2 real additions for a real data N = 2 n point DFT, comparable to the number of operations in the Split-Radix method, but with slightly fewer multiply and add operations in total. Because of the o...

We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling in the microscopic, mesoscopic and macroscopic length scales. The picture that emerges is that of a single unified framework for the study of both quantum and classical systems. While for quantum DFT, the central equation is a one-particle Schrodinger-like Kohn-Sham equation, the classical DFT cons...

In this paper we consider optimal estimators for speech enhancement in the Discrete Fourier Transform (DFT) domain. We derive an analytical solution for estimating complex DFT coefficients in the MMSE sense when the clean speech DFT coefficients are Laplacian distributed and the DFT coefficients of the noise are Gaussian or Laplacian distributed. We show that these estimators have a number of i...