Propagator descriptions of ionisation and excitation phenomena using valence bond reference functions

1992 ◽  
Vol 261 ◽  
pp. 255-264 ◽  
Author(s):  
B.T. Pickup ◽  
D.H. Mosley
Keyword(s):  
Valence Bond ◽  
Reference Functions

Resolving the Quadruple Bonding Conundrum in C2 Using Insights Derived from Excited State Potential Energy Surfaces: A Molecular Orbital Perspective

2019 ◽  
Author(s):  
Ishita Bhattacharjee ◽  
Debashree Ghosh ◽  
Ankan Paul
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Molecular Orbital ◽  
High Spin ◽  
Potential Energy Surfaces ◽  
Valence Bond ◽  
Deep Minimum ◽  
State Potential ◽  
Energy Surfaces ◽  
Mo Theory

The question of quadruple bonding in C<sub>2</sub> has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory. Here, we have systematically studied the Potential Energy Curves (PECs) of low lying high spin sigma states of C<sub>2</sub>, N<sub>2</sub> and Be<sub>2</sub> and HC≡CH using several MO based techniques such as CASSCF, RASSCF and MRCI. The analyses of the PECs for the<sup> 2S+1</sup>Σ<sub>g/u</sub> (with 2S+1=1,3,5,7,9) states of C<sub>2</sub> and comparisons with those of relevant dimers and the respective wavefunctions were conducted. We contend that unlike in the case of N<sub>2</sub> and HC≡CH, the presence of a deep minimum in the <sup>7</sup>Σ state of C<sub>2</sub> and CN<sup>+</sup> suggest a latent quadruple bonding nature in these two dimers. Hence, we have struck a reconciliatory note between the MO and VB approaches. The evidence provided by us can be experimentally verified, thus providing the window so that the narrative can move beyond theoretical conjectures.

Kekulé index for valence bond structures of conjugated systems containing cyclobutadiene

1978 ◽  
Vol 43 (5) ◽  
pp. 1375-1392 ◽  
Author(s):  
Ante Graovac ◽  
Ivan Gutman ◽  
Milan Randić ◽  
Nenad Trinajstić
Keyword(s):  
Valence Bond ◽  
Conjugated Systems

ChemInform Abstract: The Electronic Structure of Cyclooctatetraene and the Modern Valence- Bond Understanding of Antiaromaticity.

ChemInform ◽  
2010 ◽  
Vol 26 (40) ◽  
pp. no-no
Author(s):  
P. B. KARADAKOV ◽  
J. GERRATT ◽  
D. L. COOPER ◽  
M. RAIMONDI
Keyword(s):  
Electronic Structure ◽  
Valence Bond

scholarly journals Probing resonating valence bond states in artificial quantum magnets

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kai Yang ◽  
Soo-Hyon Phark ◽  
Yujeong Bae ◽  
Taner Esat ◽  
Philip Willke ◽  
...  
Keyword(s):  
Quantum Information Processing ◽  
Energy Levels ◽  
Finite Size ◽  
Valence Bond ◽  
Exchange Interactions ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Many Body ◽  
Quantum Magnets ◽  
Resonating Valence Bond

AbstractDesigning and characterizing the many-body behaviors of quantum materials represents a prominent challenge for understanding strongly correlated physics and quantum information processing. We constructed artificial quantum magnets on a surface by using spin-1/2 atoms in a scanning tunneling microscope (STM). These coupled spins feature strong quantum fluctuations due to antiferromagnetic exchange interactions between neighboring atoms. To characterize the resulting collective magnetic states and their energy levels, we performed electron spin resonance on individual atoms within each quantum magnet. This gives atomic-scale access to properties of the exotic quantum many-body states, such as a finite-size realization of a resonating valence bond state. The tunable atomic-scale magnetic field from the STM tip allows us to further characterize and engineer the quantum states. These results open a new avenue to designing and exploring quantum magnets at the atomic scale for applications in spintronics and quantum simulations.

scholarly journals The electronic structure of carbones revealed: insights from valence bond theory

2021 ◽  
Vol 23 (5) ◽  
pp. 3327-3334
Author(s):  
Remco W. A. Havenith ◽  
Ana V. Cunha ◽  
Johannes E. M. N. Klein ◽  
Francesca Perolari ◽  
Xintao Feng
Keyword(s):  
Electronic Structure ◽  
Valence Bond ◽  
Carbon Suboxide ◽  
Valence Bond Theory ◽  
Bond Theory

Valence bond theory reveals the nature of the OC–C bond in carbon suboxide and related allene compounds.

scholarly journals An Investigation into the Approximations Used in Wave Packet Molecular Dynamics for the Study of Warm Dense Matter

Plasma ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 294-308
Author(s):  
William A. Angermeier ◽  
Thomas G. White
Keyword(s):  
Molecular Dynamics ◽  
Wave Packet ◽  
Hydrogen Plasma ◽  
Valence Bond ◽  
Dense Matter ◽  
Basis Set ◽  
Warm Dense Matter ◽  
Scaling Parameters ◽  
Oppenheimer Approximation ◽  
Semi Empirical

Wave packet molecular dynamics (WPMD) has recently received a lot of attention as a computationally fast tool with which to study dynamical processes in warm dense matter beyond the Born–Oppenheimer approximation. These techniques, typically, employ many approximations to achieve computational efficiency while implementing semi-empirical scaling parameters to retain accuracy. We investigated three of the main approximations ubiquitous to WPMD: a restricted basis set, approximations to exchange, and the lack of correlation. We examined each of these approximations in regard to atomic and molecular hydrogen in addition to a dense hydrogen plasma. We found that the biggest improvement to WPMD comes from combining a two-Gaussian basis with a semi-empirical correction based on the valence-bond wave function. A single parameter scales this correction to match experimental pressures of dense hydrogen. Ultimately, we found that semi-empirical scaling parameters are necessary to correct for the main approximations in WPMD. However, reducing the scaling parameters for more ab-initio terms gives more accurate results and displays the underlying physics more readily.

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