Modeling of thermodynamic properties, like heat capacities for stoichiometric solids, includes the treatment of different sources of data which may be inconsistent and diverse. In this work, an approach based on the covariance matrix adaptation evolution strategy (CMA-ES) is proposed and described as an alternative method for data treatment and fitting with the support of data source dependent weight factors and physical constraints. This is applied to a Gibb’s Free Energy stoichiometric model for different magnesium sulfate hydrates by means of the NASA9 polynomial. Its behavior is proved by: (i) The comparison of the model to other standard methods for different heat capacity data, yielding a more plausible curve at high temperature ranges; (ii) the comparison of the fitted heat capacity values of MgSO₄·7H₂O against DSC measurements, resulting in a mean relative error of a 0.7% and a normalized root mean square deviation of 1.1%; and (iii) comparing the Van’t Hoff and proposed Stoichiometric model vapor-solid equilibrium curves to different literature data for MgSO₄·7H₂O, MgSO₄·6H₂O, and MgSO₄·1H₂O, resulting in similar equilibrium values, especially for MgSO₄·7H₂O and MgSO₄·6H₂O. The results show good agreement with the employed data and confirm this method as a viable alternative for fitting complex physically constrained data sets, while being a potential approach for automatic data fitting of substance data.

The control and prediction of morphological changes in annealed void microstructures is an essential and powerful tool for different semiconductor applications, for example, as part of the production of pressure sensors, resonators, or other silicon structures. In this work, with a focus on the void shape evolution of silicon, a novel simulation approach based on the level-set method is introduced to predict the continuous transformation of initial etched nano/micro-sized cylindrical structures at different annealing conditions. The developed model, which is based on a surface diffusion formulation and built in COMSOL Multiphysics^® (Stockholm, Sweden), is introduced and compared to experimental literature data as well as with other analytical approaches. Some advantages of the presented model include the capability of simulating other materials under similar phenomena, the simulation of any possible initial geometry, and the visualization of intermediate steps during the annealing processing.

The prediction and control of the transformation of void structures with high-temperature processing is a critical area in many engineering applications. In this work, focused on the void shape evolution of silicon, a novel algebraic model for the calculation of final equilibrium structures from initial void cylindrical trenches, driven by surface diffusion, is introduced. This algebraic model provides a simple and fast way to calculate expressions to predict the final geometrical characteristics, based on linear perturbation analysis. The obtained results are similar to most compared literature data, especially, to those in which a final transformation is reached. Additionally, the model can be applied in any materials affected by the surface diffusion. With such a model, the calculation of void structure design points is greatly simplified not only in the semiconductors field but in other engineering fields where surface diffusion phenomenon is studied.

Frequency response (FR) analysis allows the characterization of gas diffusion occurring within a porous solid system. The shape of the pressure response curves obtained after a volume modulation in the reactor gives essential information about the gas adsorption and desorption properties of the porous material, e.g., zeolites, which is in contact with a certain gas environment, as well as information about the transport phenomena such as diffusion. In this work, a simulation model developed in COMSOL Multiphysics^® is introduced to reproduce the experimental behavior of the tested solid/gas systems. This approach covers, for the first time, a coupling of computational fluid dynamics (CFD), porous media flow, and a customized mass adsorption/desorption function to simulate the behavior of real frequency response systems. The simulation results are compared to experimental data obtained from the interaction of propane in MFI zeolites as well as additional data from the literature to evaluate the model validity. Furthermore, a small variation study of the effect of simulation parameters such as the mass of the sample, bed porosity, or geometry is performed and analyzed. The essential advantage of this model with respect to other analytical approaches is to observe the spatial pressure and adsorption distribution (along with other local effects) of the gas within the porous material. Thus, local environments can be visualized, and non-idealities can, therefore, be detected in contrast to the general integral simulation approach.