CASTEP

About: CASTEP is a research topic. Over the lifetime, 666 publications have been published within this topic receiving 26241 citations.

First principles methods using CASTEP

Abstract: CASTEP Computer program / Density functional theory / Pseudopotentials / ab initio study / Plane-wave method / Computational crystallography Abstract. The CASTEP code for first principles electro- nic structure calculations will be described. A brief, non- technical overview will be given and some of the features and capabilities highlighted. Some features which are un- ique to CASTEP will be described and near-future devel- opment plans outlined.

First-principles simulation: ideas, illustrations and the CASTEP code

Abstract: First-principles simulation, meaning density-functional theory calculations with plane waves and pseudopotentials, has become a prized technique in condensed-matter theory. Here I look at the basics of the suject, give a brief review of the theory, examining the strengths and weaknesses of its implementation, and illustrating some of the ways simulators approach problems through a small case study. I also discuss why and how modern software design methods have been used in writing a completely new modular version of the CASTEP code.

Variational density-functional perturbation theory for dielectrics and lattice dynamics.

Abstract: The application of variational density functional perturbation theory (DFPT) to lattice dynamics and dielectric properties is discussed within the plane-wave pseudopotential formalism. We derive a method to calculate the linear response of the exchange-correlation potential in the GGA at arbitrary wavevector. We introduce an efficient self-consistent solver based on all-bands conjugate-gradient minimization of the second order energy, and compare the performance of preconditioning schemes. Lattice-dynamical and electronic structure consequences of space-group symmetry are described, particularly their use in reducing the computational effort required. We discuss the implementation in the CASTEP DFT modeling code, and how DFPT calculations may be efficiently performed on parallel computers. We present results on the lattice dynamics and dielectric properties of $\ensuremath{\alpha}$-quartz, the hydrogen bonded crystal $\mathrm{Na}\mathrm{H}{\mathrm{F}}_{2}$ and the liquid-crystal-forming molecule 5CB. Excellent agreement is found between theory and experiment within the GGA.

First principle investigation of halogen-doped monolayer g-C3N4 photocatalyst

Abstract: Element doping is an efficient strategy for tuning the electronic structure and improving the photocatalytic activity of graphitic carbon nitride (g-C3N4). Employing the density functional theory computation performed by CASTEP module, we investigated the band structures, electronic and optical properties of monolayer g-C3N4 doped with halogens (F, Cl, Br or I). First, the halogen atoms occupying the interstitial space enclosed by three tri-s-triazine units in the monolayer g-C3N4 unit cell was demonstrated to be the most stable configuration in terms of adsorption energy. On the basis of these interstitial-doped monolayer g-C3N4 systems, it is found that the introduction of halogen atoms leads to various density of states (DOS) and redistribution of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The F atom tends to occupy the valance band and HOMO due to its extremely high electronegativity. By contrast, the Cl, Br and I atoms are involved in the conduction band and LUMO. In sum, the calculation results show that the halogen-doped monolayer g-C3N4 systems have narrowed band gap, increased light absorption and reduced work function, which are conducive to high photocatalytic activity. The conclusions presented in this work indicate the availability of halogen-doped monolayer g-C3N4 with considerable photocatalytic performance.