Presentation Title

Anharmonicity of ice-XI Determined with the VCI and VSCF Models

Abstract

The periodic structure of crystalline materials provides an environment for quantized vibrational motion. The vibration of atoms within a crystalline lattice can give insight into properties of the crystalline material. For example, thermal properties such as heat capacity and entropy can be determined from the lattice dynamics of the crystal. Computer simulations can be used to predict these properties before attempting synthesis. Lattice dynamics are typically studied using vibrational spectroscopy, with the peaks being assigned in the vibrational spectrum via quantum-mechanical simulations. These simulations calculate the vibrational frequencies by treating the vibrations as independent harmonic oscillators. However, the harmonic oscillator model has several known limitations when describing the lattice dynamics of a crystal. Therefore, it is important to develop quantum-mechanical simulation methods that determine anharmonic vibrational states of crystals. This study presents the results of the modal analysis of ice-XI calculated with the vibrational self-consistent field (VSCF) and vibrational configuration interaction (VCI) in a developmental version of the CRYSTAL program. The VCI and VSCF models will be used to further the understanding of the properties of advanced materials.

Primary Faculty Mentor Name

Michael Ruggiero

Status

Graduate

Student College

Graduate College

Program/Major

Materials Science

Primary Research Category

Engineering & Physical Sciences

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Anharmonicity of ice-XI Determined with the VCI and VSCF Models

The periodic structure of crystalline materials provides an environment for quantized vibrational motion. The vibration of atoms within a crystalline lattice can give insight into properties of the crystalline material. For example, thermal properties such as heat capacity and entropy can be determined from the lattice dynamics of the crystal. Computer simulations can be used to predict these properties before attempting synthesis. Lattice dynamics are typically studied using vibrational spectroscopy, with the peaks being assigned in the vibrational spectrum via quantum-mechanical simulations. These simulations calculate the vibrational frequencies by treating the vibrations as independent harmonic oscillators. However, the harmonic oscillator model has several known limitations when describing the lattice dynamics of a crystal. Therefore, it is important to develop quantum-mechanical simulation methods that determine anharmonic vibrational states of crystals. This study presents the results of the modal analysis of ice-XI calculated with the vibrational self-consistent field (VSCF) and vibrational configuration interaction (VCI) in a developmental version of the CRYSTAL program. The VCI and VSCF models will be used to further the understanding of the properties of advanced materials.