Related Experiment Video
Updated: May 19, 2026
12:11
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Configuration space partitioning and matrix buildup scaling for the vibrational configuration interaction method
Andriy Samsonyuk1, Christoph Scheurer
1Lehrstuhl für Theoretische Chemie, Technische Universität München, Lichtenbergstraβe 4, 85748 Garching, Germany.
Journal of Computational Chemistry
|September 1, 2012
Summary
Accurate computation of molecular vibrational states is crucial for understanding infrared spectra. New approximate vibrational configuration interaction (VCI) schemes improve computational efficiency for large molecules.
Area of Science:
- Computational Chemistry
- Quantum Mechanics
- Spectroscopy
Background:
- Accurate computation of anharmonic vibrational states is essential for understanding molecular dynamics and nonlinear multidimensional infrared spectra.
- The vibrational configuration interaction (VCI) method is a promising approach but suffers from poor scalability with increasing system size.
Purpose of the Study:
- To analyze the scaling behavior of various approximate VCI schemes.
- To develop efficient VCI methods for medium to large molecules.
Main Methods:
- Analysis of scaling behavior of established and novel approximate VCI schemes.
- Implementation of configuration space partitioning combined with energetic thresholding and resonance screening.
Main Results:
- Identified limitations in the scalability of traditional VCI methods.
- Demonstrated that combining configuration selection, energetic thresholding, and resonance screening significantly reduces computational cost.
- Validated the accuracy of the developed approximate VCI schemes for vibrational energy calculations.
Conclusions:
- The proposed approximate VCI approach offers an efficient and accurate method for calculating vibrational states in larger molecular systems.
- This advancement facilitates deeper insights into molecular spectroscopy and dynamics.
More Related Videos
Related Concept Videos
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
03:35Hybridization of Atomic Orbitals II
sp3d and sp3d 2 Hybridization
03:24Hybridization of Atomic Orbitals I
The mathematical expression known as the wave function, ψ, contains information about each orbital and the wavelike properties of electrons in an isolated atom. When atoms are bound together in a molecule, the wave functions combine to produce new mathematical descriptions that have different shapes. This process of combining the wave functions for atomic orbitals is called hybridization and is mathematically accomplished by the linear combination of atomic orbitals. The new orbitals that...
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:38Valence Bond Theory and Hybridized Orbitals
According to valence bond theory, a covalent bond results when: (1) an orbital on one atom overlaps an orbital on a second atom, and (2) the single electrons in each orbital combine to form an electron pair. The strength of a covalent bond depends on the extent of overlap of the orbitals involved. Maximum overlap is possible when the orbitals overlap on a direct line between the two nuclei.
A σ bond (single bond in a Lewis structure) is a covalent bond in which the electron density is...
A σ bond (single bond in a Lewis structure) is a covalent bond in which the electron density is...