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Publication# First-principles investigation of the relation between structural and NMR parameters in vitreous GeO2

Abstract

NMR parameters of Ge-73 and O-17 in vitreous GeO2 and quartz GeO2, including the isotropic shifts, the quadrupole coupling constants C-Q, and the electric-field-gradient asymmetry parameters., are determined through density functional calculations. Clear correlations are established between Ge-73 shifts and the mean of the four neighboring Ge-O-Ge bond angles, and between CQ and. parameters of O-17 and the local Ge-O-Ge angle. Available experimental data for CQ and the corresponding established correlation are used to extract the value of 135 degrees for the average Ge-O-Ge angle in vitreous GeO2. The features of the Ge-O-Ge bond angle distribution of vitreous GeO2 derived in this work are consistent with those inferred from other experimental probes.

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Related concepts (4)

Density functional theory

Density-functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals, i.e. functions of another function. In the case of DFT, these are functionals of the spatially dependent electron density.

First principle

In philosophy and science, a first principle is a basic proposition or assumption that cannot be deduced from any other proposition or assumption. First principles in philosophy are from first cause attitudes and taught by Aristotelians, and nuanced versions of first principles are referred to as postulates by Kantians. In mathematics and formal logic, first principles are referred to as axioms or postulates.

Parameter

A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when identifying the system, or when evaluating its performance, status, condition, etc. Parameter has more specific meanings within various disciplines, including mathematics, computer programming, engineering, statistics, logic, linguistics, and electronic musical composition.