The past decades have seen density functional theory (DFT) evolve from a rising star in computational quantum chemistry to one of its major players. This Theme Issue, which comes half a century after the publication of the Hohenberg-Kohn theorems that laid the foundations of modern DFT, reviews progress and challenges in present-day DFT research. Rather than trying to be comprehensive, this The...

Density functional theory (DFT) provides a formally exact framework for quantum embedding. The appearance of nonadditive kinetic energy contributions in this context poses significant challenges, but using optimized effective potential (OEP) methods, various groups have devised DFT-in-DFT methods that are equivalent to Kohn-Sham (KS) theory on the whole system. This being the case, we note that...

Fastest Fourier Transform in the West (FFTW) is an adaptive FFT library that generates highly efficient Discrete Fourier Transform (DFT) implementations. It is one of the fastest FFT libraries available and it outperforms many adaptive or hand-tuned DFT libraries. Its success largely relies on the huge search space spanned by several FFT algorithms and a set of compiler generated C code (called...

In this study, we compare the single-carrier (SC) waveform adopted in IEEE 802.11ad and unique word discrete Fourier transform spread orthogonal frequency division multiplexing (UW DFT-s-OFDM) waveform. We provide equivalent representations of up-sampling and down-sampling operations of the SC waveform by using discrete Fourier transform (DFT) and inverse DFT to enable explicit comparison of th...

It is becoming evident that testability must be addressed throughout the entire design process. To successfully meet all the design goals of today's and tomorrow's enormously complex devices, swift convergence of function, timing, area and power requirements must be simultaneously accompanied by new test tools that enable rapid, predictable and repeatable DFT closure. Achieving successful DFT c...

Density-corrected DFT is a method that cures several failures of self-consistent semilocal DFT calculations by using a more accurate density instead. A novel procedure employs the Hartree-Fock density to bonds that are more severely stretched than ever before. This substantially increases the range of accurate potential energy surfaces obtainable from semilocal DFT for many heteronuclear molecu...

The goal is to reconstruct a sparse signal from some, but not all, of its Discrete Fourier Transform (DFT) values. If the signal has K non-zero and real values, a unique solution is determined by any K DFT values, their conjugates, and the DC value, if the DFT order is prime. However, no algorithm is known for this unless the K DFT values are at consecutive frequencies (a total of 2K+1 consecut...

Dispersive Fourier Transform (DFT) is a powerful technique for real-time and high-speed spectroscopy. In DFT, the spectral information of an optical pulse is mapped into time using group velocity dispersion (GVD) in the dispersive fibers with an ultrafast real-time spectral acquisition rate (>10 MHz). Typically, multi-mode fiber (MMF) is not recommended for performing DFT because the modal disp...

The day-to-day variations in epicardial defibrillation threshold (DFT) were examined in closed-chest, unanesthetized dogs. In 11 animals, DFT decreased from 15.8 +/- 2.1 J (mean +/- SE) at the beginning of the study (day 1), to 7.4 +/- 1.7 J on day 2 (p less than .0001). DFT measured daily for 5 consecutive days in seven dogs decreased from 22.1 +/- 3.1 J on day 1 to 9.3 +/- 2.3 J on day 2 (p l...