ScienceAugust 26, 2021

Jacob’s Ladder of DFT

The latest meta-GGA functional Density functional theory is at the heart of…
Avatar Victor Milman

The latest meta-GGA functional

Density functional theory is at the heart of atomistic modelling of materials. There is a huge variety of software packages that implement DFT.

The method is capable of evaluating pretty much all essential properties: mechanical, thermodynamic, electronic, optical, etc. Implementations are becoming “black box” packages, accessible to ever widening audience. BIOVIA on its own offers four different DFT-based packages!

A major question for DFT practitioners remains open:

What is the accuracy of specific DFT calculations? Can it be improved without an exorbitant computational cost?

Jacob’s Ladder

The main approximation in DFT is that of an exchange-correlation functional. We know that it is essentially a fudge, but a very successful one. And DFT can be made more accurate by including more physics in the formulation of exchange-correlation effects.

The Jacob’s ladder description refers to various levels of sophistication and hence accuracy in DFT: from local density approximation, to generalized gradient approximation (GGA), meta-GGA, hybrid functionals, etc.

The term itself was coined by Professor John Perdew – the name which is well familiar to DFT practitioners, as he is the author of many popular functionals currently in common use.

The latest addition to the collection of robust and accurate functionals is described in the paper “r2SCAN-D4: Dispersion corrected meta-generalized gradient approximation for general chemical applications” published in The Journal of Chemical Physics. This article presents a new dispersion-corrected parameterization of the meta-GGA SCAN functional – a major development that makes this functional useful for studies of weekly interacting molecular blocks. Application areas that are opening up include molecular crystals, chemical reactions in gas phase and in a solvent, molecule-surface interactions, and so on.

This new implementation is now available in TURBOMOLE, a quantum mechanics code distributed by BIOVIA.

This powerful solver has been described in detail in the last year’s review paper in The Journal of Chemical Physics, “TURBOMOLE: Modular program suite for ab initio quantum-chemical and condensed-matter simulations.”

Development and Validation

BIOVIA’s Uwe Huniar made major contributions to the r2SCAN-D4 development and validation. The new description is at least as accurate as hybrid functionals for structures of transition metal complexes, reaction energies for gas-phase reactions, and lattice energies of molecular crystals.

This latest development is available in the BIOVIA 2022 Collaborative Science Portfolio. It certainly makes TURBOMOLE ever more attractive for studies of molecular systems, including molecular crystals.

It is also likely that other solvers will adopt the new description soon, pushing the boundaries of future DFT applications.

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