Electronic structure and defect properties of B6O from hybrid functional and many-body perturbation theory calculations: A possible ambipolar transparent conductor

2014 ◽  
Vol 90 (4) ◽  
Author(s):  
J. B. Varley ◽  
V. Lordi ◽  
A. Miglio ◽  
G. Hautier
Keyword(s):  
Perturbation Theory ◽  
Electronic Structure ◽  
Transparent Conductor ◽  
Many Body ◽  
Hybrid Functional ◽  
Many Body Perturbation Theory

scholarly journals The GW Miracle in Many-Body Perturbation Theory for the Ionization Potential of Molecules

2021 ◽  
Vol 9 ◽  
Author(s):  
Fabien Bruneval ◽  
Nike Dattani ◽  
Michiel J. van Setten
Keyword(s):  
Perturbation Theory ◽  
Ionization Potential ◽  
Positive Impact ◽  
Second Order ◽  
Many Body ◽  
Hybrid Functional ◽  
Hartree Fock ◽  
Screened Exchange ◽  
Many Body Perturbation Theory ◽  
High Level

We use the GW100 benchmark set to systematically judge the quality of several perturbation theories against high-level quantum chemistry methods. First of all, we revisit the reference CCSD(T) ionization potentials for this popular benchmark set and establish a revised set of CCSD(T) results. Then, for all of these 100 molecules, we calculate the HOMO energy within second and third-order perturbation theory (PT2 and PT3), and, GW as post-Hartree-Fock methods. We found GW to be the most accurate of these three approximations for the ionization potential, by far. Going beyond GW by adding more diagrams is a tedious and dangerous activity: We tried to complement GW with second-order exchange (SOX), with second-order screened exchange (SOSEX), with interacting electron-hole pairs (WTDHF), and with a GW density-matrix (γGW). Only the γGW result has a positive impact. Finally using an improved hybrid functional for the non-interacting Green’s function, considering it as a cheap way to approximate self-consistency, the accuracy of the simplest GW approximation improves even more. We conclude that GW is a miracle: Its subtle balance makes GW both accurate and fast.

An INDO MO Study on the Ground State and the Cationic States of Cyclopentadienyl Nickel Nitrosyl

1981 ◽  
Vol 36 (12) ◽  
pp. 1361-1366 ◽  
Author(s):  
Michael C. Böhm
Keyword(s):  
Perturbation Theory ◽  
Electronic Structure ◽  
Ground State ◽  
The Self ◽  
Many Body ◽  
Self Energy ◽  
Cyclopentadienyl Ligand ◽  
Energy Part ◽  
Correct Sequence ◽  
Many Body Perturbation Theory

The electronic structure of cyclopentadienyl nickel nitrosyl (1) in the ground state as well as the cationic states of 1 are investigated by means of a semiempirical INDO Hamiltonian and many body perturbation theory. It is demonstrated that the nature of the NiNO coupling is largely covalent while the interaction between the 3d center and the cyclopentadienyl ligand is predominantly of ionic type. The ground state MO sequence of the Ni 3d orbitals is 4e2(3dx²-y²/3dxy) below 7e1(3dXz/3dyz) and 15a1(3dz2). The sequence of the ionization potentials is 8e1 (Cp - π) < 15a1<4e2<7e1. The ionization energies have been determined by means of the Green’s function formalism; the self-energy part has been calculated by a second order and a renormalized approximation. Both procedures predict the correct sequence of ionization events.

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