Sökning: "Density fitting"

Visar resultat 1 - 5 av 44 avhandlingar innehållade orden Density fitting.

1. 1. New Approaches to Large-Scale Electronic Structure Calculations

   Författare :Francesco Aquilante; Beräkningskemi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Theoretical chemistry; orbital localization; electron correlation; analytic gradients; Cholesky decomposition; density fitting; quantum chemistry; Teoretisk kemi; kvantkemi;

   Sammanfattning : Recent years have witnessed a growing interest of the scientific community for the use of ab initio and density functional theory methods in theoretical studies of molecules containing many atoms. However, the `scaling wall' of some of the most accurate of such methods is often an obstacle for their applicability to systems of real-life interest, e. LÄS MER

3. 2. Extending the Reach of Accurate Wavefunction Methods

   Författare :Mickaël G. Delcey; Roland Lindh; Per-Åke Malmqvist; Martin Schütz; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quantum chemistry; Density fitting; CASSCF; Analytical gradients; Photochemistry; X-ray spectroscopy; Kemi med inriktning mot kvantkemi; Chemistry with specialization in Quantum Chemistry;

   Sammanfattning : Multiconfigurational quantum chemistry methods, and especially the multiconfigurational self-consistent field (MCSCF) and multireference perturbation theory (MRPT2), are powerful tools, particularly suited to the accurate modeling of photochemical processes and transition metal catalysis. However, they are limited by their high computational cost compared to other methods, especially density functional theory. LÄS MER

4. 3. Thermodynamic properties of humid air and their application in advanced power generation cycles

   Författare :Xiaoyan Ji; Jinyue Yan; Umberto Desideri; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; air-water mixture; humid air; properties; wet cycles; dry air; water; enthalpy; entropy; heat capacity; density; evaporative gas turbine; compressed air energy storage; Chemical engineering; Kemiteknik;

   Sammanfattning : Water or steam is added into the working fluid (often air) in gas turbines to improve the performance of gas turbine cycles. A typical application is the humidified gas turbine that has the potential to give high efficiencies, high specific power output, low emissions and low specific investment. LÄS MER

5. 4. Constitutive models based on dislocation density : formulation and implementation into finite element codes

   Författare :Konstantin Domkin; Luleå tekniska universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Datorstödd maskinkonstruktion; Computer Aided Design;

   Sammanfattning : Correct description of the material behaviour is an extra challenge in simulation of the materials processing and manufacturing processes such as metal forming. Material models must account for varying strain, strain rate and temperature, and changing microstructure. LÄS MER

7. 5. Studies of Self-interaction Corrections in Density Functional Theory

   Författare :Guangde Tu; Olav Vahtras; Trygve Helgaker; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Theoretical chemistry; Teoretisk kemi;

   Sammanfattning : The self-interaction error (SIE) in density functional theory (DFT) appears from the fact that the residual self-interaction in the Coulomb part and that in the exchange part do not cancel each other exactly. This error is responsible for the unphysical orbital energies of DFT and the failure to reproduce the potential energy curves of several physical processes. LÄS MER