Calculation of the thermodynamic and spectroscopic quantities in molecular crystals close to the phase transitons

Kavruk, Dilan
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.


Investigation of biologically important small molecules: quantum chemical and molecular dynamics calculations
Tekin, Emine Deniz; Erkoç, Şakir; Department of Physics (2010)
In this thesis, six small molecules (S-allylcysteine, S-allyl mercaptocysteine, allicin, methyl propyl disulfide, allyl methyl sulfide and dipropylsulfide) that are found in garlic and onion, and are known to be beneficial for human health were studied using molecular mechanics, semi-empirical methods, ab-initio (Restricted Hartree Fock), and density functional theory. Using the same methods, a synthetic pyrethroid pesticide molecule, called cyfluthrin, was also studied. Structural, vibrational and electron...
Synthesis, Characterization and Evaluation of Cytotoxic Activities of Novel Aziridinyl Phosphonic Acid Derivatives
Khan, Rehan; Ulusan, Sinem; Banerjee, Sreeparna; Doğan, Özdemir (Wiley, 2019-11-01)
New aziridine 2-phosphonic acids were prepared by monohydrolysis of the aziridine 2-phosphonates that were obtained by the modified Gabriel-Cromwell reaction of vinyl phosphonate or alpha-tosylvinyl phosphonate with a primary amine or a chiral amine. The cellular cytotoxicity of these compounds was tested against the HCT-116 colorectal cancer cell lines and the CCD-18Co normal colon fibroblast lines using the MTT assay. Three of the synthesized phosphonic acid derivatives 2e (ethyl hydrogen {(2S)-1-[(1S)-1-...
Development of novel Ag/bauxite nanocomposite as a heterogeneous catalyst for biodiesel production
Bet-Moushoul, Elsie; Farhadi, Khalil; Mansourpanah, Yaghoub; Molaie, Rahim; Forough, Mehrdad; Nikbakht, Ali Mohammad (2016-07-01)
Ag/bauxite nanocomposites have been prepared using in situ reduction of aqueous AgNO3 solution in a bauxite matrix and investigated for the transesterification of sunflower oil with methanol in order to study their potential as heterogeneous catalysts. The prepared nanocopmosites were characterized by XRD, SEM, EDX, FT-IR, and TG- DTA. The Central Composite Design of the Response Surface Methodology was used to optimize the effect of reaction temperature, reaction time, catalyst loading and methanol to oil ...
Analysis of the Raman intensities near the phase transitions in ammonium halides
Yurtseven, Hasan Hamit (Elsevier BV, 2008-12-01)
This study concentrates on the temperature dependence of the Raman intensities for the lattice modes in ammonium halides (NH4Cl and NH4Br) close to phase transitions, We predict their intensities using the results of a shell model for the Raman polarizability within the framework of an Ising pseudospin-phonon coupled model.
Production of an acetone-butanol-ethanol mixture from Clostridium acetobutylicum and its conversion to high-value biofuels
Sreekumar, Sanil; Baer, Zachary C.; Pazhamalai, Anbarasan; Günbaş, Emrullah Görkem; Grippo, Adam; Blanch, Harvey W.; Clark, Douglas S.; Toste, F. Dean (Springer Science and Business Media LLC, 2015-03-01)
Clostridium acetobutylicum is a bacterial species that ferments sugar to a mixture of organic solvents (acetone, butanol and ethanol). This protocol delineates a methodology to combine solventogenic clostridial fermentation and chemical catalysis via extractive fermentation for the production of biofuel blendstocks. Extractive fermentation of C. acetobutylicum is operated in fed-batch mode with a concentrated feed solution (500 grams per liter glucose and 50 grams per liter yeast extract) for 60 h, producin...
Citation Formats
D. Kavruk, “Calculation of the thermodynamic and spectroscopic quantities in molecular crystals close to the phase transitons,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.