Q. What is SIESTA?

A. SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) is an open-source software package designed for the simulation of the electronic structure and properties of molecules and materials. It is based on Density Functional Theory (DFT) and uses a combination of numerical atomic orbitals and pseudopotentials to perform its calculations.
SIESTA is particularly known for its efficiency in handling large systems with thousands of atoms, making it a valuable tool in both academic and industrial research for studying complex materials and nanostructures.