Crystal Orbital Hamilton Populations

Chopping band structures into chemical information since 1993!

Welcome to the official (and freshly polished) COHP reference page, brought to you by the Dronskowski group at RWTH Aachen University, Germany. No matter if you're a first-time user, well experienced already, or just curious about this project of ours: Welcome on this site!

What is crystal orbital Hamilton population (COHP) analysis, in the first place? Simply speaking, it is a theoretical bond-detecting tool for solids (crystals, amorphous materials, nanostructures... allegedly, it even works for molecules!). COHP partitions the band-structure energy into orbital-pair interactions; a little more chemically speaking, it is a "bond-weighted" density-of-states between a pair of adjacent atoms. A COHP diagram indicates bonding and antibonding contributions to the band-structure energy, and it is usually plotted alongside the DOS (which just shows where electrons are, but nothing about their bonding character). Like integrating the electronic DOS gives the number of electrons in the system, an energy integral of the COHP shows the contribution of a specific contact ("bond") to the band energy: in other words, the integrated COHP hints towards the bond strength, and it comes in eV or kilojoules per mole.

No matter how complicated the structure, a COHP calculation can (in principle) be done as soon as a self-consistent electronic wavefunction has been computed, and the number of programs which support it is growing. The COHP tool extracts the important chemical information and makes it available at one glance!



While COHP analysis has been restricted to local-orbital band-structure codes (such as TB-LMTO-ASA) in the past, it is possible to project COHP (and also COOP) information from plane-wave DFT data. This has been accomplished between 2011 and now, and we proudly present the computer program LOBSTER which digests electronic-structure output from VASP, ABINIT and Quantum ESPRESSO, at present. Other codes may follow!



How exactly does this tool work? What can it do? Where can you get it? Please have a look at the following pages...