Automatic determination of important mode-mode correlations in many-mode vibrational wave functions
Carolin König1, Ove Christiansen1
1Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark.
The Journal of Chemical Physics
|April 17, 2015
Summary
New automatic methods efficiently parameterize vibrational wave functions. Optimized coordinates and flexible correlation schemes improve accuracy and efficiency for complex molecular calculations.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Molecular Spectroscopy
Background:
- Accurate parameterization of vibrational wave functions is crucial for predicting molecular properties.
- Traditional methods can be computationally intensive, limiting applications to larger systems.
Purpose of the Study:
- To develop novel automatic procedures for parameterizing vibrational coupled cluster (VCC) and vibrational configuration interaction wave functions.
- To enable system-adapted selection of mode-mode correlations for efficient and accurate calculations.
Main Methods:
- Derivation of importance measures based on Hamiltonian matrix elements and perturbative corrections.
- Implementation of a threshold-based system for automatic selection of mode-mode correlations.
- Investigation using formaldehyde, furan, and water clusters.
Main Results:
- Demonstrated accuracy comparable to standard methods for zero-point energies and infrared spectra.
- Showcased efficiency gains using optimized coordinates over normal coordinates for water clusters.
- Observed a decrease in the fraction of important correlations with increasing system size.
Conclusions:
- The developed automatic parameterization schemes offer a systematic and accurate approach to correlated many-mode vibrational wave function calculations.
- Optimized coordinates combined with flexible correlation selection enhance computational efficiency.
- These methods hold significant potential for future studies on larger and more complex molecular systems.
Related Concept Videos
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
3.9K
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to...
According to Hooke's law, the vibrational frequency is directly proportional to...
3.9K
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
2.3K
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...
2.3K
01:03Modes of Standing Waves - I
4.4K
A close look at earthquakes provides evidence for the conditions appropriate for resonance, standing waves, and constructive and destructive interference. A building may vibrate for several seconds with a driving frequency matching the building's natural frequency of vibration; this produces a resonance that results in one building collapsing while the neighboring buildings do not. Often, buildings of a certain height are devastated, while other taller buildings remain intact. This...
4.4K
01:24IR Spectroscopy: Molecular Vibration Overview
6.5K
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
6.5K
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
1.8K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.8K
01:29UV–Vis Spectroscopy: Woodward–Fieser Rules
29.9K
UV–Visible absorption spectra of conjugated dienes arise from the lowest energy π → π* transitions. The light-absorbing part of the molecule is called the chromophore, and the substituents directly attached to the chromophore are called auxochromes. A strong correlation exists between the absorption maxima, λmax, and the structure of a conjugated π system. The Woodward–Fieser rules predict the value of λmax for a...
29.9K