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In the present work, different methodologies have been used to find the gamma energy dependence of two atomic parameters of three commonly used liquid crystals, 4-Cyano-4'-pentylbiphenyl (5CB), 4-heptyl-4'-cyanobiphenyl (7CB) and 4-n-nonyl-4'-cyanobiphenyl(9CB).The atomic parameters calculated as a function of gamma energy were the effective atomic number (Zet) and effective electron density (N). This work helps to identify thecrystal which is most sensitive to gamma energies compared to the other crystals, and compares the different methods used to calculate the atomic parameters. Three different methods have been used to find the dependence of effective atomic number of the crystalson gamma energy, namely: Direct, Direct-Zef and Auto- Zef Methods. But only two of themethods, Direct and Direct-Zef, were used in this work to find the gamma energy dependence of effective electron density of the selected crystals because the Auto Zefmethod is not designed for calculating Nef. The results of Direct and Direct-Zef methodsare in good agreement with each other. The Zef as evaluated by Auto-Zef was lower thanthe Direct and Direct-Zeff predictions in the higher gamma energy region (>10MEV). In thegamma energy region, approximately between 100keV and 10MEV, all the three methodspredict that the Zff of the crystals are independent of the gamma energy. Finally, Zefdecreases as we go from 5CB through 7CB to 9CB crystals. This means that liquid crystalSCB is more affected by the radiation compared to 9CB. Therefore, the device fumishedwith 5CB crystal will have shorter life time inside reactor centers, accelerators or at anygamma radiation areas.
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