Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye
Tezin Onay Tarihi: 2011
Öğrenci: DİLAN KAVRUK
Danışman: HASAN HAMİT YURTSEVEN
Özet:We study in this thesis work the spectroscopic and thermodynamic quantities of some substances such as ammonium halides (NH4Cl, NH4I), ferroelectric crystals of tris-sarcosine calcium chloride (TSCC), tris-sarcosine calcium bromide (TSCB), organic compounds of carbon tetrachloride (CCl4) and s-triazine (C3N3H3) close to the phase transitions. Various physical and chemical properties of those materials have been measured near the critical points and have been reported in the literature. In this study, the spectroscopic parameters of the frequency shifts, intensity and bandwidths are calculated as functions of temperature or pressure near the phase transitions in ammonium halides using the experimental data from the literature. The spectroscopic parameters are related to the crystal volume and the specific heat in these compounds. The thermodynamic quantities of the specific heat, thermal expansion and the isothermal compressibility are also calculated in the solid and liquid phases of carbon tetrachloride using the experimental data. In another part of this thesis work, we analyze the temperature dependence of the spontaneous polarization and the dielectric susceptibility at fixed pressures for TSCC and TSCB by using the experimental data from the literature. The temperature dependence of the damping constant for the s-triazine is also calculated here close to the I-II transition. We use the theoretical models on the basis of the observations in the literature to calculate the critical behaviour of these physical quantities and we compare the results with the observed data. Various experimental studies in the literature give us the opportunity to find the proper way of fitting the calculated and observed results. This study gives us the chance of a better understanding of the critical behavior of the studied materials by verifying the values of some critical exponents and the types of transitions as expected by different theoretical models.