High-throughput calculations based on density functional theory (DFT) methods have been widely implemented in the scientific community. However, depending on both the properties of interest as well as particular chemical/structural phase space, accuracy even for correct trends remains a key challenge for DFT. In this work, we evaluate the use of quantum Monte Carlo (QMC) to calculate material f...

in this research, this possibility was investigated the relative stablilty geometry and bindingenergies of the hydrogen bonds of molybdate-phosphonic acid (mpa) complex in gas phase onthe basis of result of ab initio and dft calculations. three dft methods have been applied forcalculations are b3lyp, bp86 and b3pw91 that have been studied in two series of basis sets:d95** and 6-31+g(d,p) for hy...

By means of DFT-precoding, the PAPR of OFDM waveforms can be reduced. DFT-precoding has been proposed for uplink transmission in various future wireless communication systems. In this work, we consider DFT-precoding combined with spatial precoding for the uplink of multiuser MIMO OFDM systems. An efficient algorithm is developed to optimize the spatial precoder aiming at maximization of the sys...

Oligoacenes C(4n+2)H(2n+4) (n=2,...,6) are studied using a variety of ab initio methods. Density functional theory (DFT) optimized geometries were in good agreement with experiment. Vertical and adiabatic ionization potentials and electron affinities were computed with DFT and it was found that standard exchange-correlation (xc) functionals underestimate ionization potentials in oligoacenes. Po...

The performance of different DFT ~UDFT-IGLO, UDFT-GIAO, SOS-DFPT-IGLO! and hybrid-DFT approaches, as well as of HF-GIAO and MP2-GIAO methods has been compared for the calculation of O chemical shielding in the series of tetrahedral d oxo complexes MO4~M5Fe,Ru,Os!, MO4 ~M5Mn,Tc,Re!, and MO4 ~M5Cr,Mo,W!. While HF-GIAO and MP2-GIAO fail for systems with low-lying excited states ~e.g., MnO4 , CrO4 ...

The recent emergence of the discrete fractional Fourier transform (DFRFT) has caused a revived interest in the eigenanalysis of the discrete Fourier transform (DFT) matrix F with the objective of generating orthonormal Hermite-Gaussian-like eigenvectors. The Grünbaum tridiagonal matrix T – which commutes with matrix F – has only one repeated eigenvalue with multiplicity two and simple remaining...

We propose a design procedure for the real, equal-norm, lapped tight frame transforms (LTFTs). These transforms have been recently proposed as both a redundant counterpart to lapped orthogonal transforms and an infinite-dimensional counterpart to harmonic tight frames. In addition, LTFTs can be efficiently implemented with filter banks. The procedure consists of two steps. First, we construct n...

BACKGROUND Biphasic waveforms reduce defibrillation threshold (DFT) in a wide variety of models. Although there are several human studies of long-duration, high-tilt biphasic waveform defibrillation, the specific biphasic waveform shape required to achieve optimal DFT reduction is unknown. METHODS AND RESULTS This study tested the effect of single capacitor biphasic waveform tilt modification...

We introduce a new discrete fractional Fourier transform (DFrFT) based on only the DFT matrix and its powers. Eigenvectors of the DFT matrix are obtained in a simple-yetelegant and straightforward manner. We show that this DFrFT definition based on the eigentransforms of the DFT matrix mimics the properties of continuous fractional Fourier transform (FrFT) by approximating the samples of the co...

A fundamental result of free probability theory due to Voiculescu and subsequently refined by many authors states that conjugation by independent Haar-distributed random unitary matrices delivers asymptotic freeness. In this paper we exhibit many other systems of random unitary matrices that, when used for conjugation, lead to freeness. We do so by first proving a general result asserting “asym...