Optimized GGA functional for proton transfer reactions.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Standard Generalized Gradient Approximation (GGA) methods often underestimate activation barriers for proton transfer reactions.
• Accurate simulation of proton transfer is crucial for understanding various chemical and biological processes.

Purpose of the Study:

• To introduce a modified gradient-corrected BP86 functional (mBP86) for improved accuracy in calculating proton transfer reaction barriers.
• To evaluate the performance of mBP86 for chemical properties and large-scale simulations.

Main Methods:

• Reparameterization of the Becke's 1988 exchange functional using activation barriers of proton transfer reactions.
• First-principles molecular dynamics simulations of proton transfer in malonaldehyde and protonated imidazole dimer using the mBP86 functional.

Main Results:

• The mBP86 functional significantly improves the underestimation of activation barriers by standard GGA methods.
• mBP86 shows better accuracy for atomization and reaction energies compared to the parent BP86 functional.
• Simulations using mBP86 yield energy and structure evolution comparable to the widely used B3LYP functional.

Conclusions:

• The mBP86 functional represents a general improvement over the BP86 functional for various chemical properties.
• mBP86 offers a cost-effective and reliable alternative to hybrid functionals for large-scale proton transfer simulations.