Application of Density Functional Theory Based Car‐Parrinello Simulations to the Study of Catalytic Processes

Abstract

We review recent applications of density functional theory based Car-Parrinello molecular dynamics simulations to the study of the structure and reactivity of liquid superacids. We first discuss the nature of an excess proton in liquid hydrofluoric acid, which can be considered as the simplest model of a liquid superacid. Then, we analyze the origin of the superacidity of real superacids in two limiting cases, namely in boron triflouride and antimony pentafluoride in hydrofluoric acid solutions, which are one of the weakest and the strongest known superacids, respectively. We conclude by discussing some aspects of the chemical reactivity of carbon monoxide and simple hydrocarbons in SbF 5 /HF solutions.Quant. Struct.-Act. Relat., 21 (

Constrained Density Functional Theory

“…= 0 (21) where the eigencondition δW/δφ * iσ = 0 has been used. Note that only the constraint with index k remains after differentiation, even when multiple constraints are imposed on the system, and the stationary condition of the derivative being zero enforces the desired charge/spin constraints.…”

“…The separate conditions of equations (18) and (21) imply that V k and ρ must be determined self-consistently to make W stationary. This is somewhat daunting, as the Lagrangian optimization is typically only a stationary condition -that is, it is not typically a pure maximization or minimization.…”

“…18,19 The introduction of a fictitious dynamics for the orbitals in the Car-Parrinello approach 20 further reduces computational costs and has enabled density functional simulations of bioactive and reactive species. [21][22][23] The establishment of linear-response time-dependent DFT (LR-TDDFT) as a viable, and in principle exact, 24,25 formalism for obtaining excited states from DFT laid the groundwork for its routine application to excited states in organic compounds 26 and transition metal complexes. 27 Paired with a classical force field via QM/MM or ONIOM techniques, DFT and TDDFT have gained traction for computational modeling of systems once only accessible to classical simulation, such as enzymes 28 and chromophores strongly coupled to a solvent bath.…”

“…Thanks to its computational tractability, DFT has been at the forefront of efforts to extend the reach of quantum chemistry beyond the traditional realms of single-point energies and geometries in the gas phase. DFT is now routinely employed alongside spectroscopic and electrochemical analyses , and is invoked in the interpretation of novel organic and organometallic reactivity. , The favorable accuracy-to-cost ratio of approximate DFT for large systems has made it the method of choice for quantum chemical studies of biomolecular systems − and has enabled classical molecular dynamics simulations on high-dimensional Born–Oppenheimer potential energy surfaces (PES). , The introduction of a fictitious dynamics for the orbitals in the Car–Parrinello approach further reduces computational costs and has enabled density functional simulations of bioactive and reactive species. − …”