Studies of Thermodynamic Properties and Relative Stability of Polybrominated Xanthones by Density Functional Theory

The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation（△fHθ） and standard free energy of formation（△fGθ） of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution（NPBS） were discussed,and it was found that there exist high correlation between thermodynamic parameters（entropy（Sθ）,△fHθ and △fGθ） and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure（Cp,m） from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature（T,T^1 and T^2） for almost all PBXTH congeners.

Theoretical Studies on the Molecular Structures and Thermodynamic Properties of Polychlorinated Fluoranthenes

DFT-B3LYP/6-311G＊＊ method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene（PCFRT） congeners and calculate their thermo-dynamic properties in the ideal gas state,such as heat capacity at constant volume（Cv）,entropy（S）,standard enthalpy of formation（ΔfH） and standard Gibbs free energy of formation（ΔfG）.The relations of Cv,S,ΔfH and ΔfG with the number and position of chlorine atoms have also been explored,from which the relative stability of PCFRT congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation（Δr,fG）.It was found that some of the PCFRT isomers are in a nonplanar configuration and there are intramolecular Cl…Cl weak interactions in some of the isomers.With increasing the number of chlorine atoms,the values of ΔfH and ΔfG of the most stable PCFRT isomers decrease initially and then increase.The values of ΔfH and ΔfG of PCFRT congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms.The relative thermodynamic stability of PCFRT isomers is determined mainly by intramolecular adjacent Cl…Cl nuclear repulsive interaction between Cl atoms at two different six-membered rings.Most PCFRT congeners are easier to form thermodynamically than their parent compound.

Thermodynamic extremality relations in massive gravity

A universal relation between the leading correction to the entropy and extremality was proposed in the work of Goon and Penco.In this paper,we extend this work to massive gravity and investigate thermodynamic extremality relations in a topologically higher-dimensional black hole.A rescaled cosmological constant is added to the action of the massive gravity as a perturbative correction.This correction modifies the extremality bound of the black hole and leads to shifts in the mass,entropy,etc.Regarding the cosmological constant as a variable related to pressure,we obtain the thermodynamic extremality relations between the mass and entropy,pressure,charge,and parameters ci by accurate calculations.Finally,these relations are verified by a triple product identity,which shows that the universal relation exists in black holes.

Thermal properties of Lense-Thirring spacetime in tetrad theory of gravity

Using the divergence term appearing in the Lagrangian of the teleparallel equivalent of general relativity （TEGR）, we calculate the thermodynamic quantities of four tetrads＇ spacetime reproducing Lense-Thirring （LT） metric. We also investigate the first law of thermodynamics and the quantum statistical relation.