Quantum Mechanics, DFT

crystalline and molecular structure visualisation program

http://www.xcrysden.org/

SIESTA is both a method and its computer program implementation, to perform efficient electronic structure calculations and ab initio molecular dynamics simulations of molecules and solids.

http://icmab.cat/leem/siesta/

Basics of QM

http://www.cs.sandia.gov/~aematts/BasisSetsAndHamiltonians.htm