Related Experiment Video
Updated: Jul 12, 2026
09:43
Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
Published on: August 13, 2019
Variational calculation of static and dynamic vibrational nonlinear optical properties
Josep M Luis1, Miquel Torrent-Sucarrat, Ove Christiansen
1Institute of Computational Chemistry, University of Girona, Campus de Montilivi, 17071 Girona, Catalonia, Spain. josepm.luis@udg.edu
The Journal of Chemical Physics
|September 4, 2007
Summary
This study extends the vibrational configuration interaction method to calculate dynamic nonlinear optical properties. Calculations on water and ammonia molecules reveal the impact of anharmonicity on vibrational hyperpolarizabilities.
Area of Science:
- Computational chemistry
- Quantum chemistry
- Molecular spectroscopy
Background:
- Static vibrational (hyper)polarizabilities are crucial for understanding molecular responses to electric fields.
- The vibrational configuration interaction (VCI) method accurately describes molecular vibrations.
- Extending VCI to dynamic properties is essential for nonlinear optics.
Purpose of the Study:
- To extend the vibrational configuration interaction (VCI) method for calculating dynamic nonlinear optical properties.
- To investigate the influence of molecular anharmonicity on vibrational (hyper)polarizabilities.
- To assess the impact of potential energy and property surface truncations in calculations.
Main Methods:
- Extension of the vibrational configuration interaction (VCI) method.
- Infinite optical frequency approximation for dynamic properties.
- Calculations performed on H2O and NH3 molecules.
- Examination of potential energy and property surface truncations.
Main Results:
- The VCI method was successfully extended to dynamic nonlinear optical properties.
- Calculations on H2O (weak anharmonicity) and NH3 (strong anharmonicity) were performed.
- The effect of anharmonicity, particularly the umbrella mode in NH3, on vibrational (hyper)polarizabilities was analyzed.
- The impact of truncating potential energy and property surfaces was quantified.
Conclusions:
- The extended VCI method provides a robust framework for calculating dynamic nonlinear optical properties.
- Molecular anharmonicity significantly influences vibrational (hyper)polarizabilities.
- Careful consideration of surface truncations is necessary for accurate predictions.
Related Concept Videos
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
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 the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
01:10Van der Waals Equation
The ideal gas law is an approximation that works well at high temperatures and low pressures. The van der Waals equation of state (named after the Dutch physicist Johannes van der Waals, 1837−1923) improves it by considering two factors.
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
01:26The Van der Waals Equation
The ideal gas law is based on two simplifying assumptions: first, that there are no intermolecular attractions between gas molecules, and second, that the volume occupied by the molecules themselves is negligible compared with the volume of the container. However, these assumptions don't hold up under all conditions - specifically, at high pressures and low temperatures, as gas tends to deviate from ideal gas behavior.The van der Waals equation is an enhanced version of the ideal gas law,...
01:08Equation of Rotational Dynamics
Angular variables are introduced in rotational dynamics. Comparing the definitions of angular variables with the definitions of linear kinematic variables, it is seen that there is a mapping of the linear variables to the rotational ones. Linear displacement, velocity, and acceleration have their equivalents in rotational motion, which are angular displacement, angular velocity, and angular acceleration. Similar to the rotational variables, a mapping exists from Newton's second law of motion...
04:01Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation
Thus far, the ideal gas law, PV = nRT, has been applied to a variety of different types of problems, ranging from reaction stoichiometry and empirical and molecular formula problems to determining the density and molar mass of a gas. However, the behavior of a gas is often non-ideal, meaning that the observed relationships between its pressure, volume, and temperature are not accurately described by the gas laws.
01:24IR Spectroscopy: Molecular Vibration Overview
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...