SIESTA - SIESTA for the Theory of Instabilities and Transport in Functional and Low-Dimensional Materials
The project involved a consortium of five institutions for the development of the SIESTA program for efficient first-principles calculations based on density-functional theory. New important features were incorporated (such as spin-orbit coupling, multiple-lead ballistic transport, and time-dependent DFT with moving nuclei), and used in 2D and topological materials. In Nanogune special effort was done in the simulation of strongly non-equilibrium electronic processes induced by swift nuclei projectiles.
The physics of low-dimensional condensed matter has acquired renewed prominence with the advent of two-dimensional (2D) materials, such as graphene and other compounds made of exfoliable materials, and the emergence of novel behaviours, of both fundamental and applied interest, in matter confined to nano size in one, two, or three dimensions. Particularly interesting are their instabilities and transport properties. Instabilities such as those producing phase transitions, with their peculiarities in low dimensions, are of great importance in many contexts in these materials. One example is the metal-insulator transition at the interface between a thin film and a substrate of perovskite oxides, establishing a 2D electron gas (2DEG) that can couple to any ferroic property among the many known for functional perovskites (magnetic, electric, elastic) and their combinations in multiferroic systems, or exhibit superconductivity. Also, 2D transition- metal dichalcogenides offer great promise for physics and applications, as do the tailored piling of different ones. Finally, quasi-1D materials still arouse much interest, especially those in which several instabilities compete.
In this project we concentrate in the theory and simulation from first-principles of several of such systems. We will use and continue to develop the Siesta density-functional-theory program. Siesta, developed mostly in Spain, was a pioneer in extending the reach of DFT calculations to large and complex systems. Being free for academics, the program is used by over a thousand researchers world-wide, in many different scientific contexts. It remains vital, still growing in user base and features. Part of Siestas success is due to its science- driven development, through projects like this one, which coordinates most of the Siesta team in Spain and other scientists to carry out both frontier research in the above themes and the required new theoretical and methodological developments.
The following problems/systems will be addressed: Structural and transport properties of dichalcogenide 2D materials and their tailored pilings; exfoliability of di/trichalcogenides and pnictides; functional (multi-)ferroic thin films and their coupling to 2DEGs; extended defects (domain walls) and instabilities within them; interfaces of such materials with water, and water nano-confined to 1D and 2D; instabilities due to electron-phonon coupling (superconducting/ charge-density wave) in quasi-1D and 2D materials; electronic and thermal transport in nano-sized systems, and tunnelling spectroscopy for superconductors. The following theory and algorithmic new features will be coded: novel scalable solvers for the large-scale DFT Hamiltonian and advances in parallelisation and modularisation; reformalisation of the direct time-dependent DFT and of the Ehrenfest dynamics with atomic bases; development and implementation of new density functionals; implementation of density-functional perturbation theory; development of analysis tools with Wannier functions; and the implementation of full spin-orbit coupling.
This project has been funded by FIS2015-64886-C5-1-P/ MCIN/ AEI /10.13039/501100011033/ y por FEDER Una manera de hacer Europa
