Molecules in strong magnetic fields: Properties of atomic orbitals

We establish a basis set of atomic orbitals suitable to describe molecular wave functions at arbitrary magnetic field strengths and for an arbitrary orientation of the molecule relative to the magnetic field. A simple calculation for the hydrogen atom demonstrates the superiority of such an orbital over common orbitals. All types of matrix elements of the Hamiltonian of a molecule in a strong magnetic field are evaluated within our basis set of atomic orbitals.