scholarly journals Hole–hole Tamm–Dancoff-approximated density functional theory: A highly efficient electronic structure method incorporating dynamic and static correlation

2020 ◽  
Vol 153 (2) ◽  
pp. 024110 ◽  
Author(s):  
Christoph Bannwarth ◽  
Jimmy K. Yu ◽  
Edward G. Hohenstein ◽  
Todd J. Martínez
2020 ◽  
Author(s):  
Christoph Bannwarth ◽  
Jimmy K. Yu ◽  
Edward G. Hohenstein ◽  
Todd J. Martínez

<div> <div> <div> <p>The study of photochemical reaction dynamics requires accurate as well as computationally efficient electronic structure methods for the ground and excited states. While time-dependent density functional theory (TDDFT) is not able to capture static correlation, complete active space self-consistent field (CASSCF) methods neglect much of the dynamic correlation. Hence, inexpensive methods that encompass both static and dynamic electron correlation effects are of high interest. Here, we revisit hole-hole Tamm-Dancoff approximated (<i>hh</i>-TDA) density functional theory for this purpose. The <i>hh</i>-TDA method is the hole-hole counterpart to the more established particle-particle TDA (<i>pp</i>-TDA) method, both of which are derived from the particle-particle random phase approximation (<i>pp</i>-RPA). In <i>hh</i>-TDA, the <i>N</i>-electron electronic states are obtained through double annihilations starting from a doubly anionic (<i>N</i>+2 electron) reference state. In this way, <i>hh</i>-TDA treats ground and excited states on equal footing, thus allowing for conical intersections to be correctly described. The treatment of dynamic correlation is introduced through the use of commonly-employed density functional approximations to the exchange-correlation potential. We show that hh-TDA is a promising candidate to efficiently treat the photochemistry of organic and biochemical systems that involve several low-lying excited states – particularly those with both low-lying pipi* and npi* states where inclusion of dynamic correlation is essential to describe the relative energetics. In contrast to the existing literature on <i>pp</i>-TDA and <i>pp</i>-RPA, we employ a functional-dependent choice for the response kernel in <i>pp</i>- and <i>hh</i>-TDA, which closely resembles the response kernels occurring in linear response and collinear spin-flip TDDFT.</p> </div> </div> </div>


2020 ◽  
Author(s):  
Christoph Bannwarth ◽  
Jimmy K. Yu ◽  
Edward G. Hohenstein ◽  
Todd J. Martínez

<div> <div> <div> <p>The study of photochemical reaction dynamics requires accurate as well as computationally efficient electronic structure methods for the ground and excited states. While time-dependent density functional theory (TDDFT) is not able to capture static correlation, complete active space self-consistent field (CASSCF) methods neglect much of the dynamic correlation. Hence, inexpensive methods that encompass both static and dynamic electron correlation effects are of high interest. Here, we revisit hole-hole Tamm-Dancoff approximated (<i>hh</i>-TDA) density functional theory for this purpose. The <i>hh</i>-TDA method is the hole-hole counterpart to the more established particle-particle TDA (<i>pp</i>-TDA) method, both of which are derived from the particle-particle random phase approximation (<i>pp</i>-RPA). In <i>hh</i>-TDA, the <i>N</i>-electron electronic states are obtained through double annihilations starting from a doubly anionic (<i>N</i>+2 electron) reference state. In this way, <i>hh</i>-TDA treats ground and excited states on equal footing, thus allowing for conical intersections to be correctly described. The treatment of dynamic correlation is introduced through the use of commonly-employed density functional approximations to the exchange-correlation potential. We show that hh-TDA is a promising candidate to efficiently treat the photochemistry of organic and biochemical systems that involve several low-lying excited states – particularly those with both low-lying pipi* and npi* states where inclusion of dynamic correlation is essential to describe the relative energetics. In contrast to the existing literature on <i>pp</i>-TDA and <i>pp</i>-RPA, we employ a functional-dependent choice for the response kernel in <i>pp</i>- and <i>hh</i>-TDA, which closely resembles the response kernels occurring in linear response and collinear spin-flip TDDFT.</p> </div> </div> </div>


2020 ◽  
Author(s):  
Christoph Bannwarth ◽  
Jimmy K. Yu ◽  
Edward G. Hohenstein ◽  
Todd J. Martínez

<div> <div> <div> <p>The study of photochemical reaction dynamics requires accurate as well as computationally efficient electronic structure methods for the ground and excited states. While time-dependent density functional theory (TDDFT) is not able to capture static correlation, complete active space self-consistent field (CASSCF) methods are deficient in their ability to describe dynamic correlation. Hence, inexpensive methods that encompass both static and dynamic electron correlation effects are of high interest. Here, we describe the hole-hole Tamm- Dancoff approximated (<i>hh</i>-TDA) density functional theory method, which is closely related to the previously established particle-particle random phase approximation (<i>pp</i>-RPA) and its TDA variant (<i>pp</i>-TDA). In <i>hh</i>-TDA, the <i>N</i>-electron electronic states are obtained through double annihilations starting from a doubly anionic (<i>N</i>+2 electron) reference state. In this way, <i>hh</i>-TDA treats ground and excited states on equal footing, thus allowing for conical intersections to be correctly described. The treatment of dynamic correlation is introduced through the use of commonly-employed density functional approximations to the exchange-correlation potential. <i>hh</i>-TDA appears to be a promising candidate to efficiently treat the photochemistry of organic and biochemical systems that involve several low-lying excited states – particularly those with both low-lying pipi* and npi* states where inclusion of dynamic correlation is essential to describe the relative energetics. In contrast to the existing literature on <i>pp</i>-TDA, we employ a functional- dependent choice for the response kernel in <i>pp</i>- and <i>hh</i>-TDA, which closely resembles the response kernels occurring in linear response and collinear spin-flip TDDFT. </p> </div> </div> </div>


2019 ◽  
Vol 21 (44) ◽  
pp. 24478-24488 ◽  
Author(s):  
Martin Gleditzsch ◽  
Marc Jäger ◽  
Lukáš F. Pašteka ◽  
Armin Shayeghi ◽  
Rolf Schäfer

In depth analysis of doping effects on the geometric and electronic structure of tin clusters via electric beam deflection, numerical trajectory simulations and density functional theory.


2020 ◽  
Vol 3 (1) ◽  
pp. 20
Author(s):  
Valentina Ferraro ◽  
Marco Bortoluzzi

The influence of copper(I) halides CuX (X = Cl, Br, I) on the electronic structure of N,N′-diisopropylcarbodiimide (DICDI) and N,N′-dicyclohexylcarbodiimide (DCC) was investigated by means of computational DFT (density functional theory) methods. The coordination of the considered carbodiimides occurs by one of the nitrogen atoms, with the formation of linear complexes having a general formula of [CuX(carbodiimide)]. Besides varying the carbon–nitrogen bond lengths, the thermodynamically favourable interaction with Cu(I) reduces the electron density on the carbodiimides and alters the energies of the (NCN)-centred, unoccupied orbitals. A small dependence of these effects on the choice of the halide was observable. The computed Fukui functions suggested negligible interaction of Cu(I) with incoming nucleophiles, and the reactivity of carbodiimides was altered by coordination mainly because of the increased electrophilicity of the {NCN} fragments.


Author(s):  
Huimin Guo ◽  
Xiaolin Ma ◽  
Zhiwen Lei ◽  
Yang Qiu ◽  
Bernhard Dick ◽  
...  

The electronic structure and photophysical properties of a series of N-Methyl and N-Acetyl substituted alloxazine (AZs) were investigated with extensive density functional theory (DFT) and time-dependent density functional theory (TD-DFT)...


2009 ◽  
Vol 79-82 ◽  
pp. 1245-1248 ◽  
Author(s):  
Pei Lin Han ◽  
Xiao Jing Wang ◽  
Yan Hong Zhao ◽  
Chang He Tang

Electronic structure and optical properties of non-metals (N, S, F, P, Cl) -doped cubic NaTaO3 were investigated systematically by density functional theory (DFT). The results showed that the substitution of (N, S, P, Cl) for O in NaTaO3 was effective in narrowing the band-gap relative to the F-doped NaTaO3. The larger red shift of the absorption edge and the higher visible light absorption at about 520 nm were found for the (N and P)-doped NaTaO3. The excitation from the impurity states to the conduction band may account for the red shift of the absorption edge in an electron-deficiency non-metal doped NaTaO3. The obvious absorption in the visible light region for (N and P)-doped NaTaO3 provides an important guidance for the design and preparation of the visible light photoactive materials.


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