As one of the most crucial and important factors in thermodynamics (the study of the interrelation between heat and other forms of energy), enthalpy is defined as the energy or the heat content of the total system. Any chemical (or biochemical) reaction involved an exchange of energy in any form amongst the substance undergoing that reaction and their surroundings. Whenever a reaction occurs, heat energy is either utilized by that system or is given out from that system. Every reaction involves some change in the enthalpy of the total system. Without change in enthalpy, no reaction around us is possible. Changes in heat during product formation in a chemical reaction is a major cause of enthalpy generation. The enthalpy depends upon temperature, pressure and change in surroundings. The measurement of change in enthalpy is important for understanding the total mechanics of the chemical reaction. Calculation of enthalpy changes is to calculate the heat energy change when the temperature of a pure substance is changed. When it comes to change in heat, scientists typically use multiple computational chemistry techniques to decrease the uncertainty of calculations.
Figure 1. Energy profile diagrams for Al5 and Al8 clusters for the three organo-bromides obtained from DFT-M06-2X functional. Red arrow indicates ∆G, and pink arrow indicates ∆H. (Sadhukhan, T.; et al 2016)
At Alfa Chemistry, we apply density functional theory, Ab-Initio method and group contribution model to analyze chemical process and perform accurate enthalpy change calculation. According to the well-established model and a large number of calculation formulas, we provide the following enthalpy change calculation services:
- Density functional theory (DFT)
1. We combine the first principles calculation method with a novel theoretical approach for solvation to calculate the donor numbers which is important for classifying the Lewis basicity of solvents during the enthalpy change calculation.
2. Our scientists examine various levels of approximations and estimate the local molecular interactions which can not be ignored for the calculation of solvation enthalpies.
3. Moreover, the polarization effects, specfically in combination with continuum solvation approaches, are also taken into account.
4. At Alfa Chemistry, our enthalpy change calculation approach is also available for both distinct protic and aprotic solvents.
5. We also introduce G2MP2 function to calculate the enthalpy of formation by conducting the tomization energy calculation.
6. Our experts in computational chemistry can use B3LYP/B3PW91 to predict vaporation enthalpy and sublimation enthalpy.
- Ab-Initio method
We combine ab-Initio and DFT study to observe ion/radical-molecule gas-phase reactions, and we also evaluate the effect of temperature on enthalpy change.
- Group contribution model
Our teams have created a reliable group contribution model for the estimation of the sublimation enthalpies of organic compounds. The group contribution model developed is able to predict the standard molar enthalpies of sublimation with sufficient accuracy for many practical application.
Why Choose Alfa Chemistry?
- We are capable of carrying out calculation of mixing enthalpy of binary solvent mixture such as two-component systems of water and organic solvent.
- It has been proved that our calculation method is highly consistent with the experimental result.
Enthalpy change calculation provides an effective way to optimize the chemical process. Our enthalpy change calculation services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!
- Sadhukhan, T.; et al. Theoretical study of C-X [X=Cl, Br] bond activation on aluminum nanoclusters. Theoretical Chemistry Accounts. 2016, 135(10): 234.