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Optical and magnetic susceptibilities for semiconductors and alkali halides
Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
Optical and magnetic susceptibilities for semiconductors and alkali halides R.R. Reddy*, Y. Nazeer Ahammed, K. Rama Gopal, P. Abdul Azeem, D.V. Raguram, T.V.R. Rao Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, India Received 28 July 1998; received in revised form 28 October 1998
Abstract Optical susceptibility, electronic polarizability and magnetic susceptibility values have been evaluated from optical electronegativities. The validity of the proposed empirical relations has been tested in the case of II—VI, III—V group semiconductors and alkali halides. The estimated values of these parameters are in good agreement with the available experimental data. There has been no report on the direct estimation of optical susceptibility and magnetic susceptibility using the concept of optical electronegativity. 1999 Elsevier Science B.V. All rights reserved. Keywords: Optical electronegativity; Optical susceptibility; Magnetic susceptibility; Semiconductors; Alkali halides
1. Introduction Optical and magnetic susceptibilities play a vital role in understanding the structure and the nature of chemical bonding in semiconductors and ionic crystals. Van Vechten [1,2], Garbato and Manca [3] and Singh and Singh [4] have given interesting relationships between polarizability, ionicity, energy gap and interionic distance. There have been several attempts [5—15] to obtain correlation between the band gap, refractive index, optical electronegativity and electronic polarizability. Van Vechten [1,2] has established a correlation between optical susceptibility, energy gap, interionic distance and refractive index. The above studies
* Corresponding author.
directly suggest that there is a direct correlation between optical susceptibility, magnetic susceptibility, energy gap, refractive index, optical electronegativity and electronic polarizability. It has long been recognized that many of the physical properties of compound semiconductors and alkali halides are governed by the position in the periodic chart of the component atoms. Therefore, the search for the key parameters, which characterize both the individual and bond atoms, may be very useful for defining some typical properties of a given semiconductor. The optical electronegativity is a very useful parameter in understanding the nature of chemical bonding and several important physical parameters can be predicted. It has been recently suggested that a simple model [13,15] based on the concept of optical electronegativity and some other parameter should be good enough
0304-8853/99/$ — see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 9 8 ) 0 1 1 6 2 - 7
R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
for the main properties of ionic crystals and semiconductors with the use of only few numerical constants. The present paper is an attempt to study some simple correlations between optical electronegativity and alkali halides. The computed and literature [1,2,16—20] values of optical susceptibility and magnetic susceptibility show good agreement with each other.
2. Theory The concept of optical electronegativity and its use in estimating many physico-chemical parameters has been well established in Refs. [13,15,21,22]. The purpose of the present paper is to study the dependence of optical electronegativity, optical susceptibility, electronic polarizability and magnetic susceptibility in semiconductors and alkali halides. The following empirical relationships are found suitable for the estimation of optical susceptibility (s), electronic polarizability (a) and magnetic susceptibility (s ): s"0.08+[!ln(0.102*s*)]!1,, (1) where *s* is the optical electronegativity difference between the anion and cation. In the present study the electronic polarizability has been calculated using the following relation: a"0.395;10\
4.207#K M , 7.207#K o
K"ln *s*(ln *s*!4.564),
(2) (3)
where *s*, M and o are the optical electronegativity difference, molecular weight and density of the substance, respectively. The relevant data have been taken from Refs. [20—22]. Singh and Singh [17] have pointed out that magnetic susceptibility plays a vital role for the study of chemical bonding in semiconductors. Ionicity, polarizability and some other physical parameters characterize both bands and bonds in semiconductors. Good efforts have centered on correlating the above parameters, but still many uncertainties exist, calling for an accumulation of experimental and theoretical facts and do not solve how different physical parameters affect the mag-
517
netic properties of materials. Singh and Singh [17] mentioned that the refractive indices of the materials are correlated with their magnetic behavior. Reddy et al. [13,15,23] have established relation between optical electronegativity, refractive index and electronic polarizability for different materials. In our earlier paper, we established a relation between magnetic susceptibility and electronic polarizability. Experimental results in the Ref. [17] suggested that there exist a linear relation between s and a. Optical electronegativity (*s*) and a are well connected through relation (2). *s* directly illustrates the nature of the bonding. Taking Singh and Singh [17] into account, we make an attempt to correlate s and a with the following relations described elsewhere: s "!(7.82;10(a)#8.102;10\) II—VI group semiconductors,
(4)
s "!(4.56;10(a)#0.510;10\) III—V group semiconductors,
(5)
s "!(8.82;10(a)#5.020;10\) alkali halides,
(6)
where a obtained from Eq. (2) has been used in the above relations. They strongly support the view of Singh and Singh [17] that there exist a relation between magnetic susceptibility and refractive index. Moreover experimental results between s and a also indicating the linearity between them. The above relations are unique in the sense that they describe the nature of the bonding also. Such correlations have not existed so far. Only *s* provides a direct check in characterizing the nature of the bond. It is easy to estimate optical susceptibility, magnetic susceptibility and the nature of the bonding with the readily available optical electronegativities.
3. Results and discussion The computed values of optical susceptibility, electronic polarizability and magnetic susceptibility on the basis of the above proposed relations for II—VI, III—V group semiconductors and alkali halides are presented in Tables 1—3. The values of
1.05 0.80 0.70 1.15 0.90 0.80 1.15 0.90 0.80 1.15 0.90 0.80 1.05 0.80 0.70 0.70 0.45 0.35
MgS MgSe MgTe CaS CaSe CaTe SrS SrSe SrTe BaS BaSe BaTe ZnS ZnSe ZnTe CdS CdSe CdTe
0.319 0.422 0.477 0.287 0.376 0.422 0.287 0.376 0.422 0.287 0.376 0.422 0.319 0.422 0.477 0.477 0.679 0.808
0.33 0.39 — 0.28 0.33 0.42 0.27 0.31 0.38 — — — 0.32 0.39 0.50 0.33 0.38 0.49
2.40 3.96 — 0.53 0.72 1.10 0.31 0.42 0.69 — — — — — — — — —
4.47 6.17 10.37 6.21 8.04 8.67 6.96 9.17 11.22 8.33 10.39 13.00 5.38 6.70 8.00 7.87 9.86 12.47
4.56 6.05 — 6.22 7.66 8.81 6.85 8.53 10.86 8.43 9.91 12.74 5.49 6.54 8.16 7.22 8.49 10.98
Known
Present study [Eq. (2)]
Harrison (Ref. [16])
Present study [Eq. (1)]
Known (Refs. [1,2])
Electronic polarizability, a (10\ cm)
Optical susceptibility, s
Present study [Eq. (4)] !43.09 !56.41 !89.19 !56.66 !70.98 !75.92 !62.54 !79.82 !95.86 !73.25 !89.35 !109.82 !50.21 !60.55 !70.66 !69.70 !85.27 !105.64
— — — 5.90 6.98 7.53 6.85 8.15 9.95 8.64 — — 5.49 6.61 7.77 7.57 9.13 11.41
— — — !45.46 !61.15 !84.41 !57.99 !75.50 !92.96 !75.77 — — !49.18 !63.62 !67.00 !63.30 !82.00 —
Known (Refs. [17,19,20])
Magnetic susceptibility, s (10\ cm mol\) Moss (Ref. [5])
Calculated from the Clausius—Mossotti relation [(n!1)/(n#2)](M/o)"2.53;10a, taking n, M and o values from Refs. [6,20].
Optical electronegativity *s* (Refs. [21,22])
II—VI Group semiconductors
Table 1
518 R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
0.80 0.60 0.40 0.60 0.40 0.20 0.30 0.10 0.10
AlP AlAs AlSb GaP GaAs GaSb InP InAs InSb
6.03 7.33 10.51 6.68 8.11 11.10 9.48 11.51 14.07
— 0.74 0.73 0.65 0.79 1.07 0.68 0.90 1.17
0.422 0.544 0.738 0.544 0.738 1.132 0.892 1.602 1.602
Present study [Eq. (2)]
Known (Refs. [1,2])
Present study [Eq. (1)] 6.51 7.70 10.52 6.87 8.26 11.02 8.94 9.84 13.45
Known
Electronic polarizability, a (10\ cm)
Optical susceptibility, s
5.75 6.92 9.65 6.24 7.66 10.34 8.66 9.53 14.27
Moss (Ref. [5])
!28.01 !33.94 !48.44 !30.98 !37.49 !51.14 !43.74 !53.02 !64.68
Present study [Eq. (5)]
— — — !30.0 !33.3 !38.4 !45.6 !55.3 !65.9
Known (Refs. [17,19,20])
Magnetic susceptibility, s (10\ cm mol\)
Calculated from the Clausius—Mossotti relation [(n!1)/(n#2)](M/o)"2.53;10a, taking n, M and o values from Refs. [6,20].
Optical electronegativity *s* (Refs. [21,22])
III—V Group semiconductors
Table 2
R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522 519
2.95 2.05 1.85 1.55 2.95 2.05 1.85 1.55 2.90 2.00 1.80 1.50 2.95 2.05 1.85 1.55
NaF NaCl NaBr NaI KF KCl KBr KI RbF RbCl RbBr RbI CsF CsCl CsBr CsI
0.035 0.115 0.142 0.192 0.035 0.116 0.142 0.192 0.038 0.122 0.150 0.202 0.035 0.116 0.142 0.192
0.06 0.10 0.13 0.17 0.06 0.10 0.11 0.14 0.07 0.10 0.11 0.14 — — — —
0.11 0.17 0.21 0.29 0.04 0.07 0.08 0.11 0.03 0.05 0.05 0.08 — — — —
0.762 3.466 4.725 7.170 1.166 4.810 6.388 6.513 1.489 5.758 7.495 10.792 1.664 5.430 7.000 10.080
1.148 3.237 4.381 6.406 1.991 4.080 5.224 7.249 2.537 4.626 5.770 7.795 3.601 5.690 6.834 8.859
Known
Present study [Eq. (2)]
Harrison (Ref. [16])
Present study [Eq. (1)]
Known (Refs. [1,2])
Electronic polarizability, a (10\ cm)
Optical susceptibility, s
2.438 4.778 5.942 8.057 3.770 6.478 7.740 6.978 4.523 7.486 8.774 11.097 5.661 7.510 8.675 11.145
Moss (Ref. [5])
!11.74 !35.63 !46.74 !68.33 !15.32 !47.56 !61.43 !62.52 !18.17 !55.86 !71.20 !100.32 !19.72 !52.96 !66.83 !94.07
Present study [Eq. (6)]
!16.4 !30.3 !41.0 !57.0 !23.6 !39.0 !49.1 !63.8 !31.9 !46.0 !56.4 !72.2 !44.5 !86.7 !67.2 !82.6
Known (Refs. [17,19,20])
Magnetic susceptibility, s (10\ cm mol\)
Calculated from the Clausius—Mossotti relation [(n!1)/(n#2)](M/o)"2.53;10a, taking n, M and o values from Refs. [6,20].
Optical electro negativity *s*s (Refs. [21,22])
Alkali halide crystal
Table 3
520 R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
optical susceptibility (s), electronic polarizability (a) and magnetic susceptibility (s ) in the present study are in good agreement with the available experimental data. There has been no previous report on the direct estimation of optical susceptibility and magnetic susceptibility using the concept of optical electronegativity. Our estimated optical susceptibility values are in excellent agreement with the experimental values reported by Harrison [16] and also better than those of Van Vechten [1,2]. The theoretical values of optical susceptibility reported by Harrison [16] are quite erratic and become worse in the lithium and magnesium compounds when compared with experimental values. Our estimated values are in good agreement with the experimental values in the case of magnesium compounds. This indicates the soundness of the present approach. Keen observation of the results (Table 3) reveals that optical susceptibility values are increasing with decreasing optical electronegativity difference from fluorine to iodine with in common metal halides in the case of alkali halides. It can be observed from the table that as the *s* values for the group of semiconductors with common cation decrease, the optical susceptibility and electronic polarizability increases. This trend is noticed in the case of II—VI and III—V group semiconductors and alkali halides. It is pertinent to mention here that s increases with a correspond ing decrease in optical electronegativity difference for particular metal components. Careful observation of the data reveals that the estimated s values are far better in the case of CaTe, SrSe, SrTe, BaS, ZnS, ZnSe, CdSe, GaP, InP, InAs and InSb than indicated by the results of Reddy et al. [24]. It is also observed that a values increase with a corresponding increase in s . Our calculated s values agree fairly well with the experimental results. Pauling has established the nature of chemical bonding using the concept of electronegativity. *s* values are smaller for most of the semiconductors indicating that the nature of the bonding in these compounds in covalent. The *s* value is large for the alkali halides compared to that of semiconducting compounds and indicate its ionic nature. For molecule whose *s* value is large its optical susceptibility and magnetic susceptibility is less and vice-versa. The magnitude of the optical
521
and magnetic susceptibility can serve as a guide in indicating the nature of the bonding. The involvement of electronegativity in this approach has direct bearing on the concept of chemical bonding. The striking success of the present approach in describing the nature of the bonding and computing optical and magnetic susceptibility for semiconductors and alkali halides is a step forward in finding a suitable relationship between s, s , and *s*.
Acknowledgements One of the authors (R.R.R.) wishes to express his thanks to Prof. J.V. Narlikar, Director, IUCAA, Pune for his help and encouragement.
References [1] J.A. Van Vechten, Phys. Rev. 182 (1969) 891. [2] J.A. Van Vechten, Phys. Rev. 187 (1969) 1007. [3] L. Garbato, P. Manca, Chem. Phys. Lett. 48 (1977) 151. [4] V.P. Singh, S. Singh, Czech. J. Phys. B 25 (1975) 357. [5] T.S. Moss, Phys. Stat. Sol. (b) 131 (1985) 415. [6] A. Kumar, N.M. Ravindra, R. Rath, J. Phys. Chem. Solids 40 (1979) 1141. [7] R.R. Reddy, T.V.R. Rao, R. Viswanath, Proc. Ind. Natl. Sci. Acad. 55A (1989) 901. [8] R.R. Reddy, R. Viswanath, T.V.R. Rao, Proc. Ind. Natl. Sci. Acad. 56A (1990) 421. [9] R.R. Reddy, S. Anjaneyulu, Phys. Stat. Sol. (b) 174 (1992) k91. [10] R.R. Reddy, S. Anjaneyulu, R. Viswanath, Infrared Phys. 33 (1992) 385. [11] R.R. Reddy, S. Anjaneyulu, T.V.R. Rao, Infrared Phys. 33 (1992) 389. [12] R.R. Reddy, S. Anjaneyulu, C.L.N. Sharma, J. Phys. Chem. Solids 54 (1993) 635. [13] R.R. Reddy, M. Ravi Kumar, T.V.R. Rao, Infrared Phys. 34 (1993) 99. [14] R.R. Reddy, Y. Nazeer Ahammed, Infrared Phys. Technol. 36 (1995) 825. [15] R.R. Reddy, Y. Nazeer Ahammed, C.V.K. Reddy, S. Buddhudu, Crystal Res. Technol. 31 (1996) 827. [16] W.A. Harrison, Electronic Structure and the Properties of Solides, W.H. Freeman Co., San Fransisco, 1980. [17] S. Singh, P. Singh, J. Phys. Chem. Solids 41 (1980) 135. [18] D.J. Chadi, R.M. White, W.A. Harrison, Phys. Rev. Lett. 35 (1975) 1372.
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[19] Landolt-Bornstein, in: K.H. Helwege, A.M Helwege (Ed.), Eigenschaften der Materie in Inneren Aggregatzustanden, Part 10, Springer, Berlin, 1967. [20] D.R. Lide (Ed.), CRC Handbook of Chemistry and Physics, 74th ed., CRC Press, Tokyo, 1993—94. [21] J.A. Duffy, J. Phys. C. 13 (1980) 2979.
[22] J.A. Duffy, Bonding, Energy Levels and Bands in Inorganic solids, Longman Scientific and Technical, England, 1990. [23] R.R. Reddy, M. Ravi Kumar, T.V.R. Rao, Infrared Phys. 34 (1993) 95. [24] R.R. Reddy, Y. Nazeer Ahammed, M. Ravi Kumar, J. Phys. Chem. Solids 56 (1995) 825.
Optical and magnetic susceptibilities for semiconductors and alkali halides R.R. Reddy*, Y. Nazeer Ahammed, K. Rama Gopal, P. Abdul Azeem, D.V. Raguram, T.V.R. Rao Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, India Received 28 July 1998; received in revised form 28 October 1998
Abstract Optical susceptibility, electronic polarizability and magnetic susceptibility values have been evaluated from optical electronegativities. The validity of the proposed empirical relations has been tested in the case of II—VI, III—V group semiconductors and alkali halides. The estimated values of these parameters are in good agreement with the available experimental data. There has been no report on the direct estimation of optical susceptibility and magnetic susceptibility using the concept of optical electronegativity. 1999 Elsevier Science B.V. All rights reserved. Keywords: Optical electronegativity; Optical susceptibility; Magnetic susceptibility; Semiconductors; Alkali halides
1. Introduction Optical and magnetic susceptibilities play a vital role in understanding the structure and the nature of chemical bonding in semiconductors and ionic crystals. Van Vechten [1,2], Garbato and Manca [3] and Singh and Singh [4] have given interesting relationships between polarizability, ionicity, energy gap and interionic distance. There have been several attempts [5—15] to obtain correlation between the band gap, refractive index, optical electronegativity and electronic polarizability. Van Vechten [1,2] has established a correlation between optical susceptibility, energy gap, interionic distance and refractive index. The above studies
* Corresponding author.
directly suggest that there is a direct correlation between optical susceptibility, magnetic susceptibility, energy gap, refractive index, optical electronegativity and electronic polarizability. It has long been recognized that many of the physical properties of compound semiconductors and alkali halides are governed by the position in the periodic chart of the component atoms. Therefore, the search for the key parameters, which characterize both the individual and bond atoms, may be very useful for defining some typical properties of a given semiconductor. The optical electronegativity is a very useful parameter in understanding the nature of chemical bonding and several important physical parameters can be predicted. It has been recently suggested that a simple model [13,15] based on the concept of optical electronegativity and some other parameter should be good enough
0304-8853/99/$ — see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 9 8 ) 0 1 1 6 2 - 7
R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
for the main properties of ionic crystals and semiconductors with the use of only few numerical constants. The present paper is an attempt to study some simple correlations between optical electronegativity and alkali halides. The computed and literature [1,2,16—20] values of optical susceptibility and magnetic susceptibility show good agreement with each other.
2. Theory The concept of optical electronegativity and its use in estimating many physico-chemical parameters has been well established in Refs. [13,15,21,22]. The purpose of the present paper is to study the dependence of optical electronegativity, optical susceptibility, electronic polarizability and magnetic susceptibility in semiconductors and alkali halides. The following empirical relationships are found suitable for the estimation of optical susceptibility (s), electronic polarizability (a) and magnetic susceptibility (s ): s"0.08+[!ln(0.102*s*)]!1,, (1) where *s* is the optical electronegativity difference between the anion and cation. In the present study the electronic polarizability has been calculated using the following relation: a"0.395;10\
4.207#K M , 7.207#K o
K"ln *s*(ln *s*!4.564),
(2) (3)
where *s*, M and o are the optical electronegativity difference, molecular weight and density of the substance, respectively. The relevant data have been taken from Refs. [20—22]. Singh and Singh [17] have pointed out that magnetic susceptibility plays a vital role for the study of chemical bonding in semiconductors. Ionicity, polarizability and some other physical parameters characterize both bands and bonds in semiconductors. Good efforts have centered on correlating the above parameters, but still many uncertainties exist, calling for an accumulation of experimental and theoretical facts and do not solve how different physical parameters affect the mag-
517
netic properties of materials. Singh and Singh [17] mentioned that the refractive indices of the materials are correlated with their magnetic behavior. Reddy et al. [13,15,23] have established relation between optical electronegativity, refractive index and electronic polarizability for different materials. In our earlier paper, we established a relation between magnetic susceptibility and electronic polarizability. Experimental results in the Ref. [17] suggested that there exist a linear relation between s and a. Optical electronegativity (*s*) and a are well connected through relation (2). *s* directly illustrates the nature of the bonding. Taking Singh and Singh [17] into account, we make an attempt to correlate s and a with the following relations described elsewhere: s "!(7.82;10(a)#8.102;10\) II—VI group semiconductors,
(4)
s "!(4.56;10(a)#0.510;10\) III—V group semiconductors,
(5)
s "!(8.82;10(a)#5.020;10\) alkali halides,
(6)
where a obtained from Eq. (2) has been used in the above relations. They strongly support the view of Singh and Singh [17] that there exist a relation between magnetic susceptibility and refractive index. Moreover experimental results between s and a also indicating the linearity between them. The above relations are unique in the sense that they describe the nature of the bonding also. Such correlations have not existed so far. Only *s* provides a direct check in characterizing the nature of the bond. It is easy to estimate optical susceptibility, magnetic susceptibility and the nature of the bonding with the readily available optical electronegativities.
3. Results and discussion The computed values of optical susceptibility, electronic polarizability and magnetic susceptibility on the basis of the above proposed relations for II—VI, III—V group semiconductors and alkali halides are presented in Tables 1—3. The values of
1.05 0.80 0.70 1.15 0.90 0.80 1.15 0.90 0.80 1.15 0.90 0.80 1.05 0.80 0.70 0.70 0.45 0.35
MgS MgSe MgTe CaS CaSe CaTe SrS SrSe SrTe BaS BaSe BaTe ZnS ZnSe ZnTe CdS CdSe CdTe
0.319 0.422 0.477 0.287 0.376 0.422 0.287 0.376 0.422 0.287 0.376 0.422 0.319 0.422 0.477 0.477 0.679 0.808
0.33 0.39 — 0.28 0.33 0.42 0.27 0.31 0.38 — — — 0.32 0.39 0.50 0.33 0.38 0.49
2.40 3.96 — 0.53 0.72 1.10 0.31 0.42 0.69 — — — — — — — — —
4.47 6.17 10.37 6.21 8.04 8.67 6.96 9.17 11.22 8.33 10.39 13.00 5.38 6.70 8.00 7.87 9.86 12.47
4.56 6.05 — 6.22 7.66 8.81 6.85 8.53 10.86 8.43 9.91 12.74 5.49 6.54 8.16 7.22 8.49 10.98
Known
Present study [Eq. (2)]
Harrison (Ref. [16])
Present study [Eq. (1)]
Known (Refs. [1,2])
Electronic polarizability, a (10\ cm)
Optical susceptibility, s
Present study [Eq. (4)] !43.09 !56.41 !89.19 !56.66 !70.98 !75.92 !62.54 !79.82 !95.86 !73.25 !89.35 !109.82 !50.21 !60.55 !70.66 !69.70 !85.27 !105.64
— — — 5.90 6.98 7.53 6.85 8.15 9.95 8.64 — — 5.49 6.61 7.77 7.57 9.13 11.41
— — — !45.46 !61.15 !84.41 !57.99 !75.50 !92.96 !75.77 — — !49.18 !63.62 !67.00 !63.30 !82.00 —
Known (Refs. [17,19,20])
Magnetic susceptibility, s (10\ cm mol\) Moss (Ref. [5])
Calculated from the Clausius—Mossotti relation [(n!1)/(n#2)](M/o)"2.53;10a, taking n, M and o values from Refs. [6,20].
Optical electronegativity *s* (Refs. [21,22])
II—VI Group semiconductors
Table 1
518 R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522
0.80 0.60 0.40 0.60 0.40 0.20 0.30 0.10 0.10
AlP AlAs AlSb GaP GaAs GaSb InP InAs InSb
6.03 7.33 10.51 6.68 8.11 11.10 9.48 11.51 14.07
— 0.74 0.73 0.65 0.79 1.07 0.68 0.90 1.17
0.422 0.544 0.738 0.544 0.738 1.132 0.892 1.602 1.602
Present study [Eq. (2)]
Known (Refs. [1,2])
Present study [Eq. (1)] 6.51 7.70 10.52 6.87 8.26 11.02 8.94 9.84 13.45
Known
Electronic polarizability, a (10\ cm)
Optical susceptibility, s
5.75 6.92 9.65 6.24 7.66 10.34 8.66 9.53 14.27
Moss (Ref. [5])
!28.01 !33.94 !48.44 !30.98 !37.49 !51.14 !43.74 !53.02 !64.68
Present study [Eq. (5)]
— — — !30.0 !33.3 !38.4 !45.6 !55.3 !65.9
Known (Refs. [17,19,20])
Magnetic susceptibility, s (10\ cm mol\)
Calculated from the Clausius—Mossotti relation [(n!1)/(n#2)](M/o)"2.53;10a, taking n, M and o values from Refs. [6,20].
Optical electronegativity *s* (Refs. [21,22])
III—V Group semiconductors
Table 2
R.R. Reddy et al. / Journal of Magnetism and Magnetic Materials 192 (1999) 516—522 519
2.95 2.05 1.85 1.55 2.95 2.05 1.85 1.55 2.90 2.00 1.80 1.50 2.95 2.05 1.85 1.55
NaF NaCl NaBr NaI KF KCl KBr KI RbF RbCl RbBr RbI CsF CsCl CsBr CsI
0.035 0.115 0.142 0.192 0.035 0.116 0.142 0.192 0.038 0.122 0.150 0.202 0.035 0.116 0.142 0.192
0.06 0.10 0.13 0.17 0.06 0.10 0.11 0.14 0.07 0.10 0.11 0.14 — — — —
0.11 0.17 0.21 0.29 0.04 0.07 0.08 0.11 0.03 0.05 0.05 0.08 — — — —
0.762 3.466 4.725 7.170 1.166 4.810 6.388 6.513 1.489 5.758 7.495 10.792 1.664 5.430 7.000 10.080
1.148 3.237 4.381 6.406 1.991 4.080 5.224 7.249 2.537 4.626 5.770 7.795 3.601 5.690 6.834 8.859
Known
Present study [Eq. (2)]
Harrison (Ref. [16])
Present study [Eq. (1)]
Known (Refs. [1,2])
Electronic polarizability, a (10\ cm)
Optical susceptibility, s
2.438 4.778 5.942 8.057 3.770 6.478 7.740 6.978 4.523 7.486 8.774 11.097 5.661 7.510 8.675 11.145
Moss (Ref. [5])
!11.74 !35.63 !46.74 !68.33 !15.32 !47.56 !61.43 !62.52 !18.17 !55.86 !71.20 !100.32 !19.72 !52.96 !66.83 !94.07
Present study [Eq. (6)]
!16.4 !30.3 !41.0 !57.0 !23.6 !39.0 !49.1 !63.8 !31.9 !46.0 !56.4 !72.2 !44.5 !86.7 !67.2 !82.6
Known (Refs. [17,19,20])
Magnetic susceptibility, s (10\ cm mol\)
Calculated from the Clausius—Mossotti relation [(n!1)/(n#2)](M/o)"2.53;10a, taking n, M and o values from Refs. [6,20].
Optical electro negativity *s*s (Refs. [21,22])
Alkali halide crystal
Table 3
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optical susceptibility (s), electronic polarizability (a) and magnetic susceptibility (s ) in the present study are in good agreement with the available experimental data. There has been no previous report on the direct estimation of optical susceptibility and magnetic susceptibility using the concept of optical electronegativity. Our estimated optical susceptibility values are in excellent agreement with the experimental values reported by Harrison [16] and also better than those of Van Vechten [1,2]. The theoretical values of optical susceptibility reported by Harrison [16] are quite erratic and become worse in the lithium and magnesium compounds when compared with experimental values. Our estimated values are in good agreement with the experimental values in the case of magnesium compounds. This indicates the soundness of the present approach. Keen observation of the results (Table 3) reveals that optical susceptibility values are increasing with decreasing optical electronegativity difference from fluorine to iodine with in common metal halides in the case of alkali halides. It can be observed from the table that as the *s* values for the group of semiconductors with common cation decrease, the optical susceptibility and electronic polarizability increases. This trend is noticed in the case of II—VI and III—V group semiconductors and alkali halides. It is pertinent to mention here that s increases with a correspond ing decrease in optical electronegativity difference for particular metal components. Careful observation of the data reveals that the estimated s values are far better in the case of CaTe, SrSe, SrTe, BaS, ZnS, ZnSe, CdSe, GaP, InP, InAs and InSb than indicated by the results of Reddy et al. [24]. It is also observed that a values increase with a corresponding increase in s . Our calculated s values agree fairly well with the experimental results. Pauling has established the nature of chemical bonding using the concept of electronegativity. *s* values are smaller for most of the semiconductors indicating that the nature of the bonding in these compounds in covalent. The *s* value is large for the alkali halides compared to that of semiconducting compounds and indicate its ionic nature. For molecule whose *s* value is large its optical susceptibility and magnetic susceptibility is less and vice-versa. The magnitude of the optical
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and magnetic susceptibility can serve as a guide in indicating the nature of the bonding. The involvement of electronegativity in this approach has direct bearing on the concept of chemical bonding. The striking success of the present approach in describing the nature of the bonding and computing optical and magnetic susceptibility for semiconductors and alkali halides is a step forward in finding a suitable relationship between s, s , and *s*.
Acknowledgements One of the authors (R.R.R.) wishes to express his thanks to Prof. J.V. Narlikar, Director, IUCAA, Pune for his help and encouragement.
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