Calculations of the potential energy surfaces of molecular systems

1983 ◽  
Vol 24 (2) ◽  
pp. 319-320
Author(s):  
A. V. Nemukhin
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Molecular Systems ◽  
Energy Surfaces

scholarly journals Nonadiabatic Dynamics in Multidimensional Complex Potential Energy Surfaces

2020 ◽  
Author(s):  
Fábris Kossoski ◽  
Mario Barbatti
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Electron Attachment ◽  
Complex Surface ◽  
Nonadiabatic Dynamics ◽  
Surface Hopping ◽  
Molecular Systems ◽  
Out Of Plane ◽  
Dynamics Simulations ◽  
Energy Surfaces

<p>Despite the continuous development of theoretical methodologies for describing nonadiabatic dynamics of molecular systems, there is a lack of approaches for processes where the norm of the wave function is not conserved, i.e., when an imaginary potential accounts for some irreversible decaying mechanism. Current approaches rely on building potential energy surfaces of reduced dimensionality, which is not optimal for more involving and realistic multidimensional problems. Here, we present a novel methodology for describing the dynamics of complex-valued molecular Hamiltonians, which is a generalisation of the trajectory surface hopping method. As a first application, the complex surface fewest switches surface hopping (CS-FSSH) method was employed to survey the relaxation mechanisms of the shape resonant anions of iodoethene. We have provided the first detailed and dynamical picture of the p*/s* mechanism of dissociative electron attachment in halogenated unsaturated compounds, which is believed to underlie electron-induced reactions of several molecules of interest. Electron capture into the p* orbital promotes C=C stretching and out-of-plane vibrations, followed by charge transfer from the double bond into the s* orbital at the C-I bond, and, finally, release of the iodine ion, all within only 15 fs. On-the-fly dynamics simulations of a vast class of processes can be envisioned with the CS-FSSH methodology, including autoionisation from transient anions, core-ionised and superexcited states, Auger and interatomic Coulombic decay, and time-dependent luminescence.</p>

scholarly journals Nonadiabatic Dynamics in Multidimensional Complex Potential Energy Surfaces

2020 ◽  
Author(s):  
Fábris Kossoski ◽  
Mario Barbatti
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Electron Attachment ◽  
Complex Surface ◽  
Nonadiabatic Dynamics ◽  
Surface Hopping ◽  
Molecular Systems ◽  
Out Of Plane ◽  
Dynamics Simulations ◽  
Energy Surfaces

<p>Despite the continuous development of theoretical methodologies for describing nonadiabatic dynamics of molecular systems, there is a lack of approaches for processes where the norm of the wave function is not conserved, i.e., when an imaginary potential accounts for some irreversible decaying mechanism. Current approaches rely on building potential energy surfaces of reduced dimensionality, which is not optimal for more involving and realistic multidimensional problems. Here, we present a novel methodology for describing the dynamics of complex-valued molecular Hamiltonians, which is a generalisation of the trajectory surface hopping method. As a first application, the complex surface fewest switches surface hopping (CS-FSSH) method was employed to survey the relaxation mechanisms of the shape resonant anions of iodoethene. We have provided the first detailed and dynamical picture of the π*/σ* mechanism of dissociative electron attachment in halogenated unsaturated compounds, which is believed to underlie electron-induced reactions of several molecules of interest. Electron capture into the π* orbital promotes C=C stretching and out-of-plane vibrations, followed by charge transfer from the double bond into the σ* orbital at the C-I bond, and, finally, release of the iodine ion, all within only 15 fs. On-the-fly dynamics simulations of a vast class of processes can be envisioned with the CS-FSSH methodology, including autoionisation from transient anions, core-ionised and superexcited states, Auger and interatomic Coulombic decay, and time-dependent luminescence.</p>

Potential-Energy Surfaces Using Expansion Methods and Neural Networks

2012 ◽  
Author(s):  
Lionel Raff ◽  
Ranga Komanduri ◽  
Martin Hagan ◽  
Satish Bukkapatnam
Keyword(s):  
Neural Networks ◽  
Potential Energy ◽  
Basic Concept ◽  
Potential Energy Surfaces ◽  
Expansion Method ◽  
Focus Of Attention ◽  
Molecular Systems ◽  
Internal Coordinates ◽  
Energy Surfaces ◽  
Atom System

Expansion methods have been employed for some time to represent the potentialenergy surface for molecular systems. The basic concept involved with any expansion method is to write the PES expression for an N-atom system that requires the specification of 3N-6 internal coordinates as a sum of terms each of which involves fewer than N atoms and/or fewer than (3N-6) coordinate variables. Two approaches to the implementation of this concept have been suggested. In the first approach, the focus of attention is the number of internal coordinates upon which each term in the expansion depends.

scholarly journals Nonadiabatic Dynamics in Multidimensional Complex Potential Energy Surfaces

2020 ◽  
Author(s):  
Fábris Kossoski ◽  
Mario Barbatti
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Electron Attachment ◽  
Complex Surface ◽  
Nonadiabatic Dynamics ◽  
Surface Hopping ◽  
Molecular Systems ◽  
Out Of Plane ◽  
Dynamics Simulations ◽  
Energy Surfaces

<p>Despite the continuous development of theoretical methodologies for describing nonadiabatic dynamics of molecular systems, there is a lack of approaches for processes where the norm of the wave function is not conserved, i.e., when an imaginary potential accounts for some irreversible decaying mechanism. Current approaches rely on building potential energy surfaces of reduced dimensionality, which is not optimal for more involving and realistic multidimensional problems. Here, we present a novel methodology for describing the dynamics of complex-valued molecular Hamiltonians, which is a generalisation of the trajectory surface hopping method. As a first application, the complex surface fewest switches surface hopping (CS-FSSH) method was employed to survey the relaxation mechanisms of the shape resonant anions of iodoethene. We have provided the first detailed and dynamical picture of the π*/σ* mechanism of dissociative electron attachment in halogenated unsaturated compounds, which is believed to underlie electron-induced reactions of several molecules of interest. Electron capture into the π* orbital promotes C=C stretching and out-of-plane vibrations, followed by charge transfer from the double bond into the σ* orbital at the C-I bond, and, finally, release of the iodine ion, all within only 15 fs. On-the-fly dynamics simulations of a vast class of processes can be envisioned with the CS-FSSH methodology, including autoionisation from transient anions, core-ionised and superexcited states, Auger and interatomic Coulombic decay, and time-dependent luminescence.</p>

scholarly journals Potential Energy Surfaces Using Algebraic Methods Based on Unitary Groups

2011 ◽  
Vol 2011 ◽  
pp. 1-38 ◽  
Author(s):  
Renato Lemus
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Degrees Of Freedom ◽  
Traditional Approach ◽  
Unitary Groups ◽  
Algebraic Methods ◽  
Group Approach ◽  
Molecular Systems ◽  
Energy Surfaces ◽  
Algebraic Approaches

This contribution reviews the recent advances to estimate the potential energy surfaces through algebraic methods based on the unitary groups used to describe the molecular vibrational degrees of freedom. The basic idea is to introduce the unitary group approach in the context of the traditional approach, where the Hamiltonian is expanded in terms of coordinates and momenta. In the presentation of this paper, several representative molecular systems that permit to illustrate both the different algebraic approaches as well as the usual problems encountered in the vibrational description in terms of internal coordinates are presented. Methods based on coherent states are also discussed.

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