Electron configuration of the substitutional nitrogen defect in diamond

TL;DR

This paper proposes a new electron configuration model for substitutional nitrogen in diamond, supported by experimental data and theoretical modeling, challenging the traditional four-bond assumption and explaining specific vibrational features.

Contribution

It introduces a revised electron configuration for substitutional nitrogen in diamond, supported by experimental observations and a simple force constant model, which questions previous bonding assumptions.

Findings

The 1344 cm-1 band is independent of nitrogen isotopic change.

The size of substitutional nitrogen suggests a lone pair electron.

A force constant model reproduces the vibrational band with modified parameters.

Abstract

It is suggested that the substitutional nitrogen in diamonds bonded to three of the surrounding carbon atoms instead of four. This proposed electron configuration of the defect is deduced from previous experiments and theoretical considerations. Notably, the 1344 cm-1 band, characteristics of the substitutional Nitrogen, is independent of the isotopic change of Nitrogen but depend on the isotopic change of Carbon. The well established NV centre should not be stable if Nitrogen is bounded to four of the surrounding Carbon. Additional support comes from the substantially bigger size of the single substitutional nitrogen atom indicating loan pair electron. The proposed configuration of the substitutional Nitrogen was also tested by using a simple force constant model. Replacing force constant of C-N with 2/3 C-C:1/3 C=C reproduces the 1344 cm-1 band.