Confinement effects on the electronic structure of M-shell atoms: A study with explicitly correlated wave functions

2017 ◽  
Vol 117 (19) ◽  
pp. e25421 ◽  
Author(s):  
Francisco J. Gálvez ◽  
Enrique Buendía ◽  
Antonio Sarsa
Keyword(s):  
Electronic Structure ◽  
Wave Functions ◽  
Confinement Effects ◽  
Explicitly Correlated

Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems

2019 ◽  
Author(s):  
Tatiana Woller ◽  
Ambar Banerjee ◽  
Nitai Sylvetsky ◽  
Xavier Deraet ◽  
Frank De Proft ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Basis Set ◽  
Dft Methods ◽  
Molecular Switching ◽  
Wide Range ◽  
Electronic Structure Methods ◽  
Explicitly Correlated ◽  
Relative Errors ◽  
The Stability ◽  
Basis Set Expansion

<p>Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. Taking into account its size and huge conformational flexibility, DFT remains the workhorse for modeling such extended macrocycles. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, p···p stacking, steric effects, ring strain and electron delocalization. As a consequence, the selection of an exchange-correlation functional for describing the energy profile of topological switches is very difficult. For these reasons, we have examined the performance of a variety of wavefunction methods and density functionals for describing the thermochemistry and kinetics of topology interconversions across a wide range of macrocycles. Especially for hexa- and heptaphyrins, the Möbius structures have a pronouncedly stronger degree of static correlation than the Hückel and figure-eight structures, and as a result the relative energies of singly-twisted structures are a challenging test for electronic structure methods. Comparison of limited orbital space full CI calculations with CCSD(T) calculations within the same active spaces shows that post-CCSD(T) correlation contributions to relative energies are very minor. At the same time, relative energies are weakly sensitive to further basis set expansion, as proven by the minor energy differences between MP2/cc-pVDZ and explicitly correlated MP2-F12/cc-pVDZ-F12 calculations. Hence, our CCSD(T) reference values are reasonably well-converged in both 1-particle and n-particle spaces. While conventional MP2 and MP3 yield very poor results, SCS-MP2 and particularly SOS-MP2 and SCS-MP3 agree to better than 1 kcal mol<sup>-1</sup> with the CCSD(T) relative energies. Regarding DFT methods, only M06-2X provides relative errors close to chemical accuracy with a RMSD of 1.2 kcal mol<sup>-1</sup>. While the original DSD-PBEP86 double hybrid performs fairly poorly for these extended p-systems, the errors drop down to 2 kcal mol<sup>-1</sup> for the revised revDSD-PBEP86-NL, again showing that same-spin MP2-like correlation has a detrimental impact on performance like the SOS-MP2 results. </p>

Explicitly Correlated R12/F12 Methods for Electronic Structure

2011 ◽  
Vol 112 (1) ◽  
pp. 75-107 ◽  
Author(s):  
Liguo Kong ◽  
Florian A. Bischoff ◽  
Edward F. Valeev
Keyword(s):  
Electronic Structure ◽  
Explicitly Correlated

Accurate explicitly correlated wave functions for two electrons in a square

2011 ◽  
Vol 135 (1) ◽  
pp. 014106 ◽  
Author(s):  
Ilya G. Ryabinkin ◽  
Viktor N. Staroverov
Keyword(s):  
Wave Functions ◽  
Explicitly Correlated

The Electronic Structure of Closed Shell Metallocenes in the Ground State and in the Cationic Hole-States

1982 ◽  
Vol 37 (10) ◽  
pp. 1193-1204 ◽  
Author(s):  
Michael C. Böhm
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Transition Metal Complexes ◽  
Ground State ◽  
Function Method ◽  
Closed Shell ◽  
Wave Functions ◽  
Computational Framework ◽  
General Rules ◽  
Reorganization Energies

The electronic structure of tne closed shell metallocenes bis(π-cyclopentadienyl)magnesium (1), bisbenzene chromium (2), ferrocene (3) and cyclopentadienyl benzene manganese (4) has been studied in the ground state as well as in the low-lying cationic states. The computational framework is a semiempirical INDO Hamiltonian, the theoretical framework for the investigation of the cationic hole-states is the Green's function method. The calculated ionization energies are compared with the photoelectron (PE) spectra of the four closed shell metallocenes. The interrelation between theoretically determined reorganization energies and the localization properties of the orbital wave functions or the nature of the transition metal center is analyzed. General rules concerning the validity of Koopman's theorem in transition metal complexes are formulated.

Hartree–Fock calculation for the electronic structure of H+3 using numerically optimized orbitals

2001 ◽  
Vol 79 (2-3) ◽  
pp. 673-679
Author(s):  
J D Talman
Keyword(s):  
Electronic Structure ◽  
Ground State ◽  
Equilateral Triangle ◽  
Wave Functions ◽  
Equilibrium Geometry ◽  
Molecular Ion ◽  
Interatomic Spacing ◽  
Hartree Fock ◽  
Gaussian Orbitals

The Hartree–Fock wave functions for the ground state of the H2 molecule and the H+3 molecular ion are computed using radial orbitals that are numerically optimized. It is shown that these orbitals yield results comparable in accuracy to those obtained using much larger bases of Gaussian orbitals. As in previous calculations, the equilibrium geometry for H+3 is found to be that of an equilateral triangle, with an interatomic spacing of 1.64a0. PACS No.: 13.15+q

EXPLICITLY CORRELATED WAVE FUNCTIONS IN QUANTUM MONTE CARLO*

2003 ◽  
Vol 9 (1) ◽  
pp. 11-22 ◽  
Author(s):  
DARIO BRESSANINI ◽  
GABRIELE MOROSI ◽  
SILVIA TARASCO
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Wave Functions ◽  
Explicitly Correlated
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