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Using first principles calculations based on density functional theory (DFT), the electronic properties of SnO 2 bulk and thin films are studied. The electronic band structures and total energy over a range of SnO 2-multilayer have been studied using DFT within the local density approximation (LDA). We show that changing the interatomic distances and relative positions of atoms could modify the band-gap energy of SnO 2 semiconductors. Electronic-structure calculations show that band-gap engineering is a powerful technique for the design of new promising candidates with a direct band-gap. Our results present an important advance toward controlling the band structure and optoelectronic properties of few-layer SnO 2 via strain engineering, with important implications for practical device applications.

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In this paper, a combination of DFT study and Monte Carlo (MC) simulations has been performed on Gd compound which undergoes a second–order phase transition from ferromagnetic state to paramagnetic one. For this single material, the temperature-dependent total magnetization and magnetic susceptibility have been calculated and are revealed that the Curie temperature is acceptable concurrence with the experimental value. Furthermore, it was showed that under an external magnetic field of 2 Tesla (T), MCE of Gd compound around its Curie point in regard to the maximum value of magnetic entropy change ( ), agrees well with the experimental one. Besides, the Relative Cooling Power (RCP) values are found to be 34.37, 69.18, 90.74 and 128 J.kg−1 under different magnetic fields of 0.5, 1.0, 1.5 and 2T, respectively. All findings which are presented here indicate that DFT calculations and Monte Carlo simulations can be efficiently used to predict the magnetic and magnetocaloric features of Gd and related alloys.