Sains Malaysiana 39(2)(2010): 281–283
Ab Initio Calculations of Vibrational Frequencies in a Glassy State of
Selenium
(Pengiraan Ab Initio bagi Frekuensi Getaran pada
Selenium Berkeadaan Kaca)
Ahmad Nazrul Rosli*, Hasan Abu Kassim & Keshav N. Shrivastava
Jabatan
Fizik, Fakulti Sains, Universiti Malaya
50603 Kuala
Lumpur, Malaysia
Diserahkan:
19 Mei 2009 / Diterima: 29 Julai 2009
ABSTRACT
We used the density functional theory to calculate the
vibrational frequencies of clusters of atoms. We obtained the bond distances
and angles for which the energy of the Schršdinger equation is minimum. We
found the bond distance between two Se atoms to be 232.1 pm when double zeta
wave function was used. The frequency of oscillations was calculated to be
325.3 cm-1 but the intensity was zero because Se2 molecules were present in a very small
number. When polarised double zeta wave function (DZP) was used, the bond length of Se2 was found to be 223.1 pm and the frequency is 367.4 cm-1. Similarly for other clusters of
selenium, we calculated the frequencies and compared with the experimental
data. The experimental Raman spectra give 250 cm-1 for a selenium glass. By comparing the experimental frequencies
with those calculated we found that linear Se3 was present in the glass. This indicates the possibility of
linear growth in the glass.
Keywords: Density functional theory; glass; raman spectra;
selenium; vibrational frequencies
ABSTRAK
Kami menggunakan teori fungsi ketumpatan untuk membuat pengiraan
bagi frekuensi getaran bagi kelompok atom. Apabila tenaga persamaan Schršdinger
diminimumkan, kami dapat mengukur panjang ikatan dan sudut bagi atom-atom.
Panjang ikatan bagi dua atom Se adalah 232.1 pm dengan menggunakan fungsi
ikatan zeta berganda. Frekuensinya adalah 325.3 cm-1 tetapi keamatannya adalah sifar disebabkan kehadiran sangat
sedikit molekul Se2. Apabila fungsi gelombang zeta berganda
berkutub digunakan, panjang ikatan adalah 223.1 pm dan frekuensinya adalah 367.4
cm-1. Sama juga bagi kelompok selenium yang
lain, kami mendapatkan frekuensi gelombang untuk dibandingkan dengan data
eksperimen. Data eksperimen bagi spektrum Raman menunjukkan nilai 250 cm-1 bagi kaca selenium. Perbandingan dengan
data eksperimen menunjukkan Se3 linear
wujud dalam kaca. Ini menunjukkan kemungkinan pertumbuhan secara linear dalam
kaca.
Kata kunci: Frekuensi getaran; kaca; spektrum Raman; selenium;
teori fungsi ketumpatan
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*Pengarang untuk surt-menyurat; email:
anazrul84@yahoo.com