Topic

# Adiabatic process

About: Adiabatic process is a research topic. Over the lifetime, 20751 publications have been published within this topic receiving 408945 citations.

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TL;DR: In this paper, a modification of the exchange functional introduced by Perdew and Wang was proposed, which significantly enlarges its field of applications and allows to obtain remarkable results both for covalent and noncovalent interactions.

Abstract: Starting from an analysis of the low-density and large gradient regions which dominate van der Waals interactions, we propose a modification of the exchange functional introduced by Perdew and Wang, which significantly enlarges its field of applications. This is obtained without increasing the number of adjustable parameters and retaining all the asymptotic and scaling properties of the original model. Coupling the new exchange functional to the correlation functional also proposed by Perdew and Wang leads to the mPWPW model, which represents the most accurate generalized gradient approximation available until now. We next introduce an adiabatic connection method in which the ratio between exact and density functional exchange is determined a priori from purely theoretical considerations and no further parameters are present. The resulting mPW1PW model allows to obtain remarkable results both for covalent and noncovalent interactions in a quite satisfactory theoretical framework encompassing the free elec...

2,952 citations

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TL;DR: In this paper, the authors present theory, implementation, and validation of excited state properties obtained from time-dependent density functional theory (TDDFT), based on a fully variational expression for the excited state energy, a compact derivation of first order properties is given.

Abstract: This work presents theory, implementation, and validation of excited state properties obtained from time-dependent density functional theory (TDDFT). Based on a fully variational expression for the excited state energy, a compact derivation of first order properties is given. We report an implementation of analytic excited state gradients and charge moments for local, gradient corrected, and hybrid functionals, as well as for the configuration interaction singles (CIS) and time-dependent Hartree–Fock (TDHF) methods. By exploiting analogies to ground state energy and gradient calculations, efficient techniques can be transferred to excited state methods. Benchmark results demonstrate that, for low-lying excited states, geometry optimizations are not substantially more expensive than for the ground state, independent of the molecular size. We assess the quality of calculated adiabatic excitation energies, structures, dipole moments, and vibrational frequencies by comparison with accurate experimental data for a variety of excited states and molecules. Similar trends are observed for adiabatic excitation energies as for vertical ones. TDDFT is more robust than CIS and TDHF, in particular, for geometries differing significantly from the ground state minimum. The TDDFT excited state structures, dipole moments, and vibrational frequencies are of a remarkably high quality, which is comparable to that obtained in ground state density functional calculations. Thus, yielding considerably more accurate results at similar computational cost, TDDFT rivals CIS as a standard method for calculating excited state properties in larger molecules.

1,976 citations

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TL;DR: In this article, the detailed structure of the interaction of a strong stellar wind with the interstellar medium is presented, including the effects of thermal conduction between the hot interior and the cold shell of swept-up interstellar matter.

Abstract: The detailed structure of the interaction of a strong stellar wind with the interstellar medium is presented. First, an adiabatic similarity solution is given which is applicable at early times. Second, a similarity solution is derived which includes the effects of thermal conduction between the hot (about 1 million K) interior and the cold shell of swept-up interstellar matter. This solution is then modified to include the effects of radiative energy losses. The evolution of an interstellar bubble is calculated, including the radiative losses. The quantitative results for the outer-shell radius and velocity and the column density of highly ionized species such as O VI are within a factor 2 of the approximate results of Castor, McCray, and Weaver (1975). The effect of stellar motion on the structure of a bubble, the hydrodynamic stability of the outer shell, and the observable properties of the hot region and the outer shell are discussed.

1,652 citations

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TL;DR: Relativistic gravitational collapse equations assuming spherical symmetry, adiabatic flow and pressure gradient forces were proposed in this paper, where spherical symmetry was assumed to be a function of the density.

Abstract: Relativistic gravitational collapse equations assuming spherical symmetry, adiabatic flow and pressure gradient forces

1,442 citations

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TL;DR: In this paper, a hybrid Hartree−Fock−density functional (HF-DF) model called the modified Perdew−Wang 1-parameter model for kinetics (MPW1K) was optimized against a database of 20 forward barrier heights.

Abstract: A new hybrid Hartree−Fock−density functional (HF-DF) model called the modified Perdew−Wang 1-parameter model for kinetics (MPW1K) is optimized against a database of 20 forward barrier heights, 20 r...

1,418 citations