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Showing 1 to 20 of 22 for “"generalized gradient"”.
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Multiscale ab initio approaches to materials physics
… final chapter we combine this method with the generalized gradient approximation to perform calculations on high-pressure phases of boron.
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Theoretical Investigations of the Structural, Dynamical, Electronic, Magnetic, and Thermoelectric Properties of CoRhYSi (Y = Cr, Mn) Quaternary Heusler Alloys
… are addressed using Perdew–Burke and Ernzerhof's generalized gradient approximation (GGA-PBE). With the exception of CoRhCrSi and CoRhMnSi, which are simple ferromagnets that are approximately half metallic in nature, electronic structure calculations demonstrate that these compounds have a gap in …
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Models for transition metal oxides and for protein design
… methods such as the Local Density (LDA) or Generalized Gradient Approximation (GGA). However, known problems exist when using these methods for predicting the electronic structure and total energy of transition metal oxides. We demonstrate that the LDA+U method, in which localized d …
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Computational modelling of the electronic and structural properties of chalcopyrite-type semiconductors and platinum group metal chalcogenides
… used the Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA) energy exchange correlation functionals within DFT as implemented in the Quantum Espresso (QE) computer simulation package. The results from these two functionals predicted band gaps which were greatly …
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Spin waves in doped graphene
… ubiquitous local density approximation (LDA), generalized gradient approximation (GGA), and all of their descendants are examples that implicitly use the electron gas reference system. Orbital based approximations such as Slater and Singwi-Tosi-Land-Sjolander provide an alternative that use no …
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TDDFT calculations for excitation spectra of solids and superstructures utilizing mGGA
… potential functional given by meta-generalized gradient approximation(mGGA). Our theoretical results were compared to WIEN2K’s, and good agreement was obtained. As the application, we apply TDDFT plus mGGA to calculate optical spectra for bulk solids. The result shows good agreement …
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Density functional theory study of adsorption of cronconate dyes on TiO2 Anatase (010) and (100) surfaces
… using a plane-wave pseudo potential method. The generalized gradient approximation (GGA) was used in the scheme of Perdew-Burke Ernzerhof to describe the exchange -correlation function as implemented in the CASTEP package in Material Studio of BIOVIA. The adsorption results shows a spontaneous …
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Computational structure analysis of multicomponent oxides
… results of calculations making use of both the Generalized Gradient Approximation (GGA) to DFT and GGA with Hubbard U correction (GGA+U). This enabled us to study how hole localization, or delocalization, on Co affects the ground states and order-disorder transition temperatures of the system. …
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Construction of first-principles density functional approximations and their applications to materials
… surface. Further, this work demonstrates why generalized gradient approximations (GGAs) are often able to describe some properties of sp-bonded narrow-gap insulators well. A Laplacian-level pure-density functional is developed with the goal of describing metallic condensed matter. This …
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Ab initio computational applications to complex biomolecular systems
… accuracy, the scheme of implementing the generalized gradient approximation (GGA) exchangecorrelation functionals into the Orthogonalized Linear Combination of Atomic Orbitals (OLCAO) program suite has been discussed, and the computational efficiency has been analyzed correspondingly. …
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Linear scaling density functional theory with Gaussian orbitals and periodic boundary conditions
… energy, our code also computes analytic energy gradients with respect to atomic positions and cell dimensions (forces). Combining the latter with the developed in this work redundant internal coordinate algorithm for optimization of periodic systems, it becomes possible to optimize geometries of …
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DESCRIPTION OF POLARONS IN LAYERED TRANSITION METAL OXIDES USING THE r2SCAN DENSITY FUNCTIONAL WITH FULLY NONLOCAL CORRECTIONS AND EFFECT OF STRAIN ON THE BAND GAP OF MONOLAYER MOLYBDENUM DISULFIDE
… on a free-standing MoS2 monolayer using the generalized gradient approximation (GGA) PBE, the hybrid functional HSE06, and many-body perturbation theory with the GW approximation using PBE wavefunctions (G0W0@PBE). Our findings indicate that under biaxial strain with the experimental …
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Degradation of Cd-yellow pigment: an ab initio study of defects and adsorption of oxygen and water on CdS
… of the Density Functional Theory (DFT) in the Generalized Gradient Approximation (GGA-PBE) with the use of ultrasoft pseudopotentials. Despite the standard DFT-GGA ensures a correct order of electronic states, the G0W0 calculations are strongly required to attribute an accurate position of the …
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First-principles modeling of thermal stability and morphology control of cathode materials in Li-ion batteries
… of 3d transition metal oxides using the generalized gradient approximation (GGA) to density functional theory and GGA+ U method. Two substantial contributions to the error in GGA oxidation energies are identified. The first contribution originates from the overbinding of GGA in the O₂ …
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Role of sulfur in vibration spectra and bonding and electronic structure of GeSi surfaces and interfaces
… approach is used with the local density (LDA), generalized gradient (GGA) approximations and van der Waals (vdW) interactions. The frozen phonon method was used to calculate the vibrational mode frequencies of these surfaces. The calculated frequencies produce stretch, bond bending and wag …
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A theoretical investigation in heterogeneous gold catalysis
… functional theory (DFT) calculations, within the generalized-gradient approximation (GGA), were performed to investigate the change in nobility of gold from the extended surface to small clusters. Potential methanol synthesis intermediates were optimized on the Au(111) surface. It was found that …
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Mutual information-based gradient-ascent control for distributed robotics
… class of decentralized mutual information-based gradient-ascent controllers that continuously move robots equipped with sensors to better observe their environment. We begin with the fundamental problem of deploying a single ground robot equipped with a range sensor and tasked to build an …
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The Effect of Zr-Doping and Crystallite Size on the Mechanical Properties of TiO2 Rutile and Anatase
… density approximation (LDA) and two types of generalized gradient approximations (GGA), using the formulations by Perdew, Bunge and Enzerhoff, referred to as PBE, and by Wu and Cohen, reffered to as WC. The zero pressure volumes are predicted smaller by <3% in LDA computations and larger by 8 …
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From Hartree Product to Kohn-Sham and Beyond: Exploring Self-Interaction in Self-Consistent Field Methods
… functionals improve upon GGAs more than meta-generalized gradient approximations (GGAs) do, and range-separated functionals are much better - though not completely solving the problem. Having addressed SIE in biomolecules in terms of where charges comes from and where it goes, we finally …
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Thermomechanical properties of novel lanthanum zirconate based thermal barrier coatings - an integrated experimental and modeling study
… including furnace cycling test, thermal gradient mechanical fatigue test, and jet engine thermal shock test. The results show that for the layered TBCs, porous YSZ + LZ has reasonably good thermal cycling performance. For the composite TBCs, LZ/8YSZ (vol. % is 50:50) with a thin buffer …
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