Conference On Molecules to Materials: ICMM2006

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Early Research Studies on:"Explaining the trends of Nuclear Shielding caused by Magnetic moments related to Susceptibilties" have been detailed at the webpages at the URL: http://saravamudhan.tripod.com/ 

This link is to dispaly the Copy of manuscript of Paper in Indian Journal of Physics, Vol.79(9), p 985-989 (2005) which is a special issue for the Symposium on "Condensed Matter Days 2004":

The title of Paper: "MAGNETIZED MATERIALS: CONTRIBUTIONS INSIDE LORENTZ ELLIPSOIDS"

An International Conference

held at SLIET, Longowal, Punjab, INDIA during March3-6,2006

 

Bulk solid specimen shape dependences in the molecular, chemical-shift tensor determinations

 

(the Figures in this article are included as ".jpg" images and mouse-over messages appear when the cursor is placed over the images !)

For an elaboration on the intramolecular aspects of induced fileds (measured as Chemical shifts) Click on Link: http://www.geocities.com/amudhan20012000/ismar_ca98.html

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Abstract

 

Determination1 of the chemical shift tensors (measured with respect to a ‘reference’ chemical-compound) require using single crystals of organic molecules and these are diamagnetic specimen. The chemical shifts arise due to variations in induced fields at a proton (nuclear) site within a molecule, due to the changes in the electron charge circulations within the molecules when placed in a strong external magnetic field. The solid-state High Resolution Proton Magnetic Resonance (HR PMR) techniques yield tensor values measured experimentally, but it becomes necessary to calculate and take into consideration the intermolecular contributions to the chemical shifts to retrieve the only ‘intra molecular’ shift tensor values. The intermolecular contributions in principle can be contribution beginning from the molecule which is immediate neighbor and the other molecules which are distant neighbors extending to the entire extent of the macroscopic specimen. Thus it raises the questions pertinent for taking into consideration the induced fields from the entire bulk of the specimen at a point within the specimen which typically are the issues in the study of magnetic materials. Seeking answers to such questions  is necessary to validate the procedures used for the retrieval of the intra molecular values as mentioned above. These questions and, the answers seem to pave the way to secure certain clarifications pertaining to field distributions within magnetized materials. Thus evolving a criterion to correct for the bulk specimen shape dependences in the context of the measurement of proton Chemical Shift Tensor paves the way to unravel the consequences of induced field distributions within the material medium. This path-way, from molecule to materials, seem to be refreshing the understanding of  the requirements laid out for the specifications of local fields at points within a specimen with bulk magnetization features.

 

 

1.INTRODUCTION

 

In diamagnetic molecules the electrons, which are all spin-paired, undergo circulatory motions centered on the atomic nuclei in the molecular frame-work. In the case of diamagnetic molecular systems, there are two electrons in each of the occupied molecular orbital. The occupancies in molecular orbitals entails the possibility that the charge circulations of the electrons in the orbitals can be in the opposite directions. Thus even though there are continuous circulations of electrons there can be cancellations of the induced fields because of the circulations in opposite directions. When an external magnetic field is applied, there can be preferences established for circulations in one direction over the other alternative direction and there could be changes in the velocity of circulations and the circulation paths. Such effects in the environment of bonded atoms can have varying effects significant enough to indicate the electronic structures. It is primarily these differences in induced fields which are of interest to chemists while investigating spectroscopically, and, in particular using the NMR Spectroscopic tool.

The situation described above, for a diamagnetic molecule, is entirely with respect to the intra molecular perspectives for induced fields at the site of nuclei. What compounds this description of induced field at particular site is the fact that there are contributions to induced fields from other molecules. There are molecules which are in the immediate vicinity as well as from the distant locations in a continuous distribution over the entire macroscopic extent of the specimen, which at any particular instance, can be a single crystal of organic molecule. Under the influence of external magnetic field the electronic circulations prevailing are the same in every one of the independently identifiable equivalent molecules which are present in the crystal. The induced fields due to a molecule at a given site differ depending upon whether that specified site is occupied by a proton bonded to that molecule or in any molecule located in any of the other the lattice sites.

It is a fact that the induced fields arising at a site, due to the specified repeating-unit of the electronic structure in the lattice (which is a molecule in the particular case), must be considered always inseparably with the induced fields from the other lattice site units. This makes the estimation of induced fields for a given site to become complicated and laborious to evaluate. While approximations are resorted to, then the uncertainties in the calculated estimates in conjunction with the accuracies of experimental measurements render the interpretations to be less conclusive.

 

This is the text of the Full Paper for the presentation made at the Sant Longowal Institute of Technology, Longowal, Sangrur, Punjab, INDIA on the occasion of the "International Conference on Molecules to Materials" - The ICMM2006 held during March 3-6, 2006.

Click on the link below to display a webpage with links to contributions to events during July 2005 to February 2006. http://saravamudhan.tripod.com/id12.html#BOTTOM

The contents of pages: index, id1, id2, id3, & id4 of this ite contain the text of the
Full Paper appearing in the Proceedings of ICMM2006 March 3-6, 2006
Section on Materials for the Furure page 13-18; Article #2.3
 
The contents of page id5 is the Abstract for EPISTEME-2
 
The contents of page id6 is on EUROMAR2006