## What is/are First Principles Methods?

First Principles Methods - These simulations are based on a two-step procedure where (i) the molecular properties (vibrational frequencies, IR and Raman intensities) are evaluated using first principles methods and (ii) the three-layer model is employed to calculate the macroscopic responses using these molecular responses, the geometry of the experimental setup, and the optical properties of the layers.^{[1]}Description of nanosystems with first principles methods of quantum mechanics is still a cumbersome process, hence simpler models are rather used in the process of modeling.

^{[2]}Here we study the structural, elastic, electronic, vibrational and thermodynamic properties of hexagonal XAl2O4 (X?=?Cd, Ca and Sr) spinels with space group P63 using first principles methods.

^{[3]}Anisotropic thermal expansion coefficients of tetragonal γ-TiAl and hexagonal α2-Ti3Al phases were calculated using first principles methods.

^{[4]}Theoretical calculations based on First principles methods were employed to calculate the electronic structures and magnetic properties of Cu doping and zinc and oxygen vacancies behavior of Zn1−xCuxO.

^{[5]}Here, we review how a selection of computational tools, including first principles methods, classical molecular dynamics and enhanced sampling techniques, are contributing to construct a picture of how pLGICs function and can be pharmacologically targeted to treat the disorders they are responsible for.

^{[6]}Starting with first principles methods, a sequence of simulation methods can be applied to calculate the maximum possible coercive field and expected energy density product of a magnet made from a novel magnetic material composition.

^{[7]}Realistic finite temperature simulations of matter are a formidable challenge for first principles methods.

^{[8]}The adsorption energy, the electron charge and the magnetic moment were calculated through first principles methods.

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## density functional theory

We employ first principles methods based on density functional theory and beyond to study CdSexTe1−x alloys in the zincblende and wurtzite structures.^{[1]}We use the first principles methods based on density functional theory to study the hydrogen storage capacity of Na-decorated two dimensional (2D) boron monolayer (BM).

^{[2]}We study the phase stability, mechanical properties, and electronic structure of two quasi-binary ceramic systems, Ti1-xScxN and Ti1-xYxN (0 ≤ x ≤ 1), using first principles methods based on density functional theory, cluster expansion formalism, and Monte Carlo techniques.

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