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Title: Molecular dynamic simulations, {sup 6}Li solid state NMR and ultraphosphate glasses

Abstract

The author's laboratory continues to use NMR to investigate the structure and dynamics in amorphous materials, including the local structure of ultraphosphate glasses. Changes in the alkali environment in these phosphate glasses as a function of modifier concentration has recently been probed using {sup 6}Li and {sup 23}Na solid state NMR. Molecular dynamic (MD) simulations have also been performed in an attempt to gain additional insight into the variations of the local structure. Interestingly, although there are distinct variations in the Li coordination number as well as the Li-O bond lengths in the MD simulations (with a minimum or maximum in these parameters near the 20% Li{sub 2}O concentration), a linear change in the {sup 6}Li NMR chemical shift is observed between 5 and 50% Li{sub 2}O mole fraction. One would expect that such variations should be observable in the NMR chemical shift. In an attempt to understand this behavior the author has performed empirical calculation of the {sup 6}Li NMR chemical shift directly from the structures obtained in the MD simulations. It has been argued that the NMR chemical shift of alkali species can be related to a chemical shift parameter A, where A is defined as the summationmore » of the shift contributions for all the oxygens located within the first (and possibly the second) coordination sphere around the cation. For the present case of Li phosphate glasses, the chemical shift correlates directly to the bond valence of the coordinating oxygen.« less

Authors:
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
755586
Report Number(s):
SAND2000-1098J
TRN: AH200021%%34
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Journal Name:
NMR Newsletter
Additional Journal Information:
Other Information: Submitted to NMR Newsletter; PBD: 1 May 2000
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; PHOSPHATE GLASS; MOLECULAR STRUCTURE; NUCLEAR MAGNETIC RESONANCE; LITHIUM OXIDES; CHEMICAL SHIFT; COMPUTERIZED SIMULATION; MOLECULAR DYNAMICS METHOD

Citation Formats

ALAM,TODD M. Molecular dynamic simulations, {sup 6}Li solid state NMR and ultraphosphate glasses. United States: N. p., 2000. Web.
ALAM,TODD M. Molecular dynamic simulations, {sup 6}Li solid state NMR and ultraphosphate glasses. United States.
ALAM,TODD M. Mon . "Molecular dynamic simulations, {sup 6}Li solid state NMR and ultraphosphate glasses". United States. https://www.osti.gov/servlets/purl/755586.
@article{osti_755586,
title = {Molecular dynamic simulations, {sup 6}Li solid state NMR and ultraphosphate glasses},
author = {ALAM,TODD M.},
abstractNote = {The author's laboratory continues to use NMR to investigate the structure and dynamics in amorphous materials, including the local structure of ultraphosphate glasses. Changes in the alkali environment in these phosphate glasses as a function of modifier concentration has recently been probed using {sup 6}Li and {sup 23}Na solid state NMR. Molecular dynamic (MD) simulations have also been performed in an attempt to gain additional insight into the variations of the local structure. Interestingly, although there are distinct variations in the Li coordination number as well as the Li-O bond lengths in the MD simulations (with a minimum or maximum in these parameters near the 20% Li{sub 2}O concentration), a linear change in the {sup 6}Li NMR chemical shift is observed between 5 and 50% Li{sub 2}O mole fraction. One would expect that such variations should be observable in the NMR chemical shift. In an attempt to understand this behavior the author has performed empirical calculation of the {sup 6}Li NMR chemical shift directly from the structures obtained in the MD simulations. It has been argued that the NMR chemical shift of alkali species can be related to a chemical shift parameter A, where A is defined as the summation of the shift contributions for all the oxygens located within the first (and possibly the second) coordination sphere around the cation. For the present case of Li phosphate glasses, the chemical shift correlates directly to the bond valence of the coordinating oxygen.},
doi = {},
journal = {NMR Newsletter},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {5}
}