Improving and developing simulation techniques are key to obtaining higher efficiency and accuracy in molecular simulations of dense liquid systems. The methodology development introduced in this thesis is relevant both for academia and industrial applications. In this thesis, the methods developments/improvements for molecular simulations are introduced followed by applications for realistic systems and systems of industrial relevance....

Undoubtedly, materials that can be tuned on a molecular level offer tremendous opportunities. However, to understand and customize such materials is challenging. In this context, molecular simulation can be helpful. The work presented in this thesis deals with two types of materials, Metal-Organic Frameworks and Ionic Liquids, and the study with molecular simulation to determine their potential for specific gas separations. For the prediction of their behavior and relevant materials properties with molecular simulation, force fields of sufficient quality are required..