Xiamen Valence Bond (XMVB) is a modern highly efficient quantum chemistry program for performing electronic structure calculations based on valence bond (VB) theory. It provides an elegant way to faithfully represent classical VB theory, in which Heitler-London-Slater-Pauling (HLSP) functions built on non-orthogonal atomic orbitals serve as state functions. XMVB implements all modern ab initio VB methods, such as VBSCF, SCVB, BLW, BOVB, VBCI, VBPT2, DFVB. It allows to compute many useful quantities for chemical interpretation, such as relative weights of chemical structures resonance energies, diabatic states, etc.
The Natural Bond Orbital (NBO) program NBO 7.0 is a discovery tool for chemical insights from complex wavefunctions. NBO 7.0 is the current version of the broad suite of 'natural' algorithms for optimally expressing numerical solutions of Schrödinger's wave equation in the chemically intuitive language of Lewis-like bonding patterns and associated resonance-type 'donor-acceptor' interactions. NBO plays well with most popular electronic structure programs; currently there are 16 NBO-affiliated programs and protected interfaces.
Using a wavefunction generated by many available quantum mechanical programs, irrespective whether based on GTO, STO, or numerical atomic orbitals, DGrid generates an equidistant grid of values. More than 40 different functions can be evaluated. The resulting field can be searched for localization domains or basins, together with the corresponding critical points and interconnection lines. Specific functions can be integrated over the basins yielding all the descriptors useful for the bonding analysis. For instance, to each ELI-D basin can be assigned a population of electrons within, or, after the evaluation of overlap integrals, the delocalization indices between different QTAIM basins can be computed. Additionally, the real space analysis can be combined with the orbital analysis by the calculation of domain natural (or Fermi) orbitals or perform the isopycnic transformation QTAIM basins to learn about the covalent bond order.
DGrid can be used with single determinantal wavefunctions (HF/KS) as well as with explicitly correlated density matrices from a multireference CI calculation. Since the version 5.0 also the solid state wavefunction from the FHI-aims code can be utilized.
MoProSuite is a software package dedicated to the charge density modeling of crystal structures. It is constituted by two main computational components (MoPro and VMoPro), themselves interfaced by convenient graphical user interfaces (MoProGUI and MoProViewer, respectively).
MoPro is a crystallographic refinement and molecular modeling package. It allows structural and charge density studies of crystal structures of variable sizes, ranging from small molecules to biological macromolecules. It implements the Hansen & Coppens multipolar atom model of electron density. This is necessary to take into account the deformation of electron density arising from the interatomic interactions.
Tonto is a software library for performing crystallographic and quantum chemical calculations.
Its purpose is to facilitate the combination of both these in close collaboration. The unique feature of Tonto is its ability to refine the positions and ADPs in a molecular wavefunction (representing a fragment of a molecular crystal) to experimentally measured X-ray structure factors. Tonto can also refine Kohn-Sham or Hartree-Fock molecular orbitals to the same X-ray data. Tonto can produce a range of density, density-matrix, and
energy related properties useful for understanding chemical bonding. Tonto is used as the back-end for the popular CrystalExplorer and Olex2 programs. It is written in an object oriented language Foo which translated top modern Fortran, and it is open source, licensed under the lesser GPL.
CrystalExplorer embodies the full suite of tools associated with the popular Hirshfeld surface analysis. With access to a quantum chemistry program like Gaussian, it enables mapping of various properties on molecular surfaces, calculation of intermolecular interaction energies, lattice energies, and the topology of intermolecular interactions in a molecular crystal via energy frameworks.
NCIPlot is a software for revealing non covalent interactions (hydrogen bonds, steric clashes, halogen bonds, van der Waals, etc) from the electron density. This can be done from the outcome of calculations (molecular or periodic) as well as from the geometry (promolecular densities) and even from X-ray data (XD).
The program suites are free of charge and can be downloaded, along with exercises.