Theoretical Study On The Thermal Reaction Enthalpy Of Metal Composite Oxide Aluminum

Because of its high temperature resistance,good chemical stability,metal composite oxides(MCOs)has an irreplaceable position in the field of functional materials,such as laser materials and piezoelectric materials.In recent years,with the development of MCOs'application,it was found that using MCOs as a combustion catalyst in propellant would greatly increasing the burning rate,reducing the pressure exponent,and making the reaction more stable.Therefore,it is necessary to recognize the thermodynamic properties of them.However,due to the excellent stability of MCOs and the limitation of the current detection technology,there is no systematic method to predict their thermodynamic parameters.Based on the MCOs' molecular model,this paper has studied the relationship between crystalline phases and thermodynamic parameters through MCOs' unit cell structure,electron kinetic energy,nuclear energy,electron repulsion energy and electron exchange energy by the means of(DFT)method,and the main contents and conclusions are as following:The GGA-PBE/DNP,GGA-PW91/DNP and GGA-BLYP/DNP were used for unit cell optimization and structural analysis for various crystalline phases of seven oxides.Total energy E were studied to calculate the thermit reaction enthalpies of common oxides.Compared calculated resluts with the experiment values,the GGA-PBE/DNP which has the minimum mean deviation was selected to calculate the MCOs' thermit reaction enthalpies.The results indicats that their thermit reaction enthalpies are various based on the same functional and basis set,which show that the transform of crystal structure will lead to the change of properties.The thermit reaction enthalpies of the same perfect crystal of oxides is inequal based on the different functional and basis set.Compared with experiment values,the result values calculated at the GGA-PBE function conjuction with DNP basis set have the minimums absolute error,root mean square error and the highest linear fitting constant.It is known that the accuracy of the functional and basis set is the highest.In the GGA-PBE/DNP level of theory,we can get the thermit reaction enthalpies(?rHm)of four series of MCOs at their perfect crystal,and compare the calculated(?rHm)to the thermit reaction enthalpies of physical mixing of metal oxides with the same amount of substance.The main conclusions are as following:Among MCOs,the maximum and minimum deviation of the thermit reaction enthalpies and their physical mixing are tungstate and ferrite crystals,respectively.The results shown that the heat release followed by the formation of MCOs of ferrite series is the lowest.According to the calculated(?fHm)and the known Cp,m of oxides,standard molar enthalpy of reaction(?fHm(?))of metal complex oxides was solved with Kirchhoff formula,and their standard molar enthalpy of formation was finally calculated.The formation enthalpies(?fHm)of four series of MCOs were calculated according to the Hess's law and the?rHm obtained through the Kirchhoff formula,their standard molar enthalpy of formation was calculated.Through the linear fitting results of calculated MCOs' standard molar enthalpy of formation and the reference values,it is known that correlation coefficient are all above 0.95,which means linear fitting results are very precise.Furthermore,the calculated formation enthalpy(?fHm)of NiMoO4,CuMoO4,PbZrO3(Pm3m),PbZrO3(Pba2),PbZrO3(Pbam),MgZrO3,CdZrO3,MnZr03,CuWO4,Fe2W06 were-1078.75,-1058.45,-1343.87,-1266.54,-1342.29,-1333.03,-1210.43,-1388.05,-1131.07,-1860.11 kJ·mol-1,which were never been reported before.