Recommendation systems have become extremely common in recent years. It helps the customer to discover information and settle on choices where they do not have the required learning to judge a specific item. It can be utilized as a part of different diverse approaches to encourage its customer with effective information sorting. It is a software tool and techniques that provide suggestion based on the customer's taste to discover new appropriate thing for them by filtering personalized information based on the user's preferences from a large volume of information. Users taste and preferences should be constructed accurately in order to provide most relevant suggestions. This survey paper compare's and details the various type of recommender system and popular recommendation algorithms and its uses.

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The journey of theoretical study of semiconductors is reviewed in nonconventional way. We have started with the basic introduction of Hartree-Fock method and introduce the fundamentals of Density Functional Theory (DFT). From the oldest Local density approximations (LDA) to the most recent developments of semi-local corrections [Generalised Gradient Approximation (GGA), Meta-GGAs], Hybrid functionals and Orbital dependent methodologies are discussed in detail. During this discussion, we have defined the relevant and widely used terms in methodological and applicational DFT. To showcase the performance of DFT, results obtained via different approximations are compared. We indicate the success of semilocal approximations in structural properties prediction. We also show how less computationally costly but withstand architecture of some semi-local DFT methods can solve the long riddle of bandgap underestimation. In semiconductor physics, the importance of not only the band structure prediction, but also proper calculation of Fermi energy and exact finding of band alignment is argued. This provides the guideline for the proper choice of methods for investigation of structural, electronic and optical properties. The comparison of Fermi energy dependent properties can channelize the theoretical studies on modern age environment-friendly researches on semiconductors, like artificial photocatalysis, energy efficient opto-electronic devices, etc. This prescription on proper choice of DFT method is potential competent to complement the experimental findings as well as can open up a pathway of advanced semiconducting material discoveries.