scholarly journals Core excitations with excited state mean field and perturbation theory

2020 ◽  
Vol 153 (15) ◽  
pp. 154102 ◽  
Author(s):  
Scott M. Garner ◽  
Eric Neuscamman
Keyword(s):  
Perturbation Theory ◽  
Excited State ◽  
Mean Field ◽  
Core Excitations

Perturbation theory of the pair correlation function in molecular fluids

1978 ◽  
Vol 56 (5) ◽  
pp. 571-580 ◽  
Author(s):  
R. L. Henderson ◽  
C. G. Gray
Keyword(s):  
Perturbation Theory ◽  
Correlation Function ◽  
Pair Correlation Function ◽  
Pair Correlation ◽  
Mean Field ◽  
Pair Potential ◽  
Harmonic Series ◽  
Harmonic Space ◽  
Potential Symmetries ◽  
Harmonic Components

We study the perturbation theory of the angular pair correlation function g(rω1ω2)in a molecular fluid. We consider an anisotropic pair potential of the form u = u0 + ua, where u0 is an isotropic 'reference' potential, and for simplicity in this paper we assume the perturbation potential ua to be 'multipole-like', i.e., to contain no l = 0 spherical harmonics. We expand g in powers of ua about g0, the radial distribution function appropriate to u0. This series is examined by expanding ha = h−h0 (where h = g−1) and its corresponding direct correlation function ca in spherical harmonic components. We consider approximate summations of the series in ua that automatically truncate the corresponding harmonic series, so that the Ornstein–Zernike (OZ) equation relating ha and ca can be solved in closed form. We first expand ca = c1 + c2 + … where cn includes all terms in ca of order (ua)n. Taking ua to be a quadrupole–quadrupole interaction, we find that a 'mean field' (MF) approximation ca = c1 gives rise to only three nonvanishing harmonic components in ha, so that OZ is solved explicitly in Fourier space. The MF solution for multipoles of general order is given in an appendix. Graphical methods are then used to identify the class of all terms in the ua series that are restricted to the harmonic space defined by MF. A portion of this class can be summed by solving OZ with the closure ca = −βg0ua + h0(ha−ca), where β = (kT)−1, h0 = g0−1 This system is designated as generalized MF (GMF), and solved by numerical iteration. Numerical results from MF and GMF are presented for quadrupolar ua, taking u0 to be a Lennard-Jones potential. Symmetries imposed by the restricted harmonic space are foreign to the full g, yet harmonics within this space are sufficient for evaluation of many macroscopic properties. The results are therefore evaluated in harmonic form by comparison with the corresponding harmonic components of the 'correct' g as evaluated by Monte Carlo simulation.

Photodynamic behavior of electronic coupling in a N-methylformamide dimer

2015 ◽  
Vol 17 (18) ◽  
pp. 12356-12364
Author(s):  
Martina Zámečníková ◽  
Dana Nachtigallová
Keyword(s):  
Perturbation Theory ◽  
Excited State ◽  
Electronic Coupling ◽  
Water Molecules ◽  
Complete Active Space ◽  
Active Space ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field

The role of the bridging water molecules has been studied during the excited state photodynamics of a N-methylformamide dimer in complex with water molecules employing the complete active space self-consistent field (CASSCF) and CAS perturbation theory (CASPT2) methods.

scholarly journals Effects of quantum confinement on excited state properties ofSrTiO3fromab initiomany-body perturbation theory

2016 ◽  
Vol 94 (4) ◽  
Author(s):  
Sebastian E. Reyes-Lillo ◽  
Tonatiuh Rangel ◽  
Fabien Bruneval ◽  
Jeffrey B. Neaton
Keyword(s):  
Perturbation Theory ◽  
Excited State ◽  
Quantum Confinement

scholarly journals Dynamical Mean Field within Iterative Perturbation Theory

2007 ◽  
Vol 111 (501.) ◽  
pp. 753-761 ◽  
Author(s):  
B. Radzimirski ◽  
R.J. Wojciechowski
Keyword(s):  
Perturbation Theory ◽  
Mean Field

scholarly journals Решетки населенностей, создаваемые в газе атомов водорода с помощью ультрафиолетовых аттосекундных импульсов

2021 ◽  
Vol 129 (5) ◽  
pp. 627
Author(s):  
Р.М. Архипов ◽  
М.В. Архипов ◽  
А.В. Пахомов ◽  
Ю.М. Артемьев ◽  
Н.Н. Розанов
Keyword(s):  
Perturbation Theory ◽  
Approximate Solution ◽  
Excited State ◽  
Modulation Depth ◽  
Single Atom ◽  
Hydrogen Atoms ◽  
Central Frequency ◽  
Nonresonant Excitation ◽  
First Excited State ◽  
Attosecond Pulses

The possibility of population density grating in a gas of hydrogen atoms using a pair ultraviolet (UV) attosecond pulses that do not overlap in the medium is studied. Wherein the central frequency of the pulses can both coincide with the frequency of the resonant transition 1−2 from the main state in the first excited state (the main line of the Lyman series), and be detuned from it. The results of numerical calculations are in agreement with the analytical values ​​obtained on the basis of approximate solution of Schrödinger equation using perturbation theory. It is shown that under resonant excitation the greatest efficiency of the grating is achieved with an increase in the pulse duration. When nonresonant excitation, on the contrary, the system is more efficiently excited by short quasi-unipolar subcycle pulses than bipolar multicycle pulses. The results obtained can be applicable to coherent excitation of a single atom (thin layer) using a pair of UV pulses. The possibility of controlling the modulation depth of the gratings by changing the carrier envelope phase (CEP) of attosecond pulses is shown.

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