Sains Malaysiana 42(7)(2013): 955–959

Topology of Electron Density of Cadmium Telluride Determined

from Relief and Contour Plots

(Topologi Ketumpatan Elektron Kadmium Telurida daripada Lakaran Timbul dan Lakaran Kontur)

A.P. Othman* & G.A. Gopir

School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 Bangi, Selangor, D.E. Malaysia

Diserahkan: 13 Jun 2012/Diterima: 15 November 2012

ABSTRACT

The topology of the electron density yields a faithful and a reliable mapping of the concepts of atoms, molecular structure, bonds and structure, besides providing the basis for a theory of structural stability. In quantum mechanics and in particular quantum chemistry, the electron density is a measure of the probability of an electron occupying an infinitesimal element of space surrounding any given point. Contour plots of electron density distribution of cadmiun telluride (CdTe) were obtained using the density functional theory (DFT) method and were used as the basis to qualitatively study the bond, structure and stability of the molecule when it is in bulk. We looked at the way the electron density, ρ of CdTe defines the gradient field and hence the bonding type. We identified the bond paths that coincide with the contours of electron sharing. These bond paths indicated that the molecule was slightly covalent. Our topological analysis led us to conclude that CdTe was an n-type semiconductor with covalent bond and slight ionic character.

Keywords: Bonding; DFT; electron density; molecular structure; topology

ABSTRAK

Topologi ketumpatan elektron memberikan maklumat yang sahih dan pemetaan yang baik bagi menerangkan konsep atom, struktur molekul, ikatan dan struktur selain daripada memberikan asas kepada teori kestabilan struktur. Dalam mekanik kuantum, khususnya kimia kuantum, ketumpatan elektron memberikan kiraan keberangkalian sesuatu elektron menghuni satu ruang terhingga, di sekeliling sesuatu titik. Lakaran kontour taburan ketumpatan elektron kadmium telurid telah didapati dengan menggunakan kaedah teori ketumpatan fungsian (DFT) dan telah diguna sebagai asas untuk mengkaji ikatan, struktur dan kestabilan molekul dalam keadaan pukal. Penyelidikan ke atas taburan ketumpatan, ρ CdTe yang membentuk medan kecerunan membolehkan kita menentukan jenis ikatan. Kami mengenal pasti laluan ikatan antara atom Cd dan Te yang memerihalkan perkongsian elektron. Laluan ikatan ini menandakan molekul tersebut memiliki ikatan kovalen yang lemah. Analisis topologi merumuskan CdTe sememangnya semikonduktor jenis-n yang memiliki ikatan kovalen dengan sedikit ikatan ionik.

Kata kunci: DFT; ikatan; ketumpatan elektron; struktur molekul; topologi

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*Pengarang untuk surat-menyurat; email: puaad@ukm.my