Novel Molecular-Dynamics-Based Protocols for Phase Space Sampling in Complex Systems.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Spectroscopy

Background:

• Accurate simulation of chromophore optical and photophysical properties requires thorough phase space exploration.
• Vibrational motion and molecular environment coupling are crucial factors.
• Non-adiabatic molecular dynamics, particularly surface hopping, necessitates representative conformational snapshots.

Purpose of the Study:

• To introduce novel molecular dynamics (MD) protocols for phase space sampling.
• To address limitations of existing methods like Wigner distribution sampling for anharmonic systems.
• To improve the accuracy of internal energy distribution and force fields in MD simulations.

Main Methods:

• Development of two new protocols: "local temperature adjustment" and "individual QM/MM-based relaxation."
• Application of these protocols to phase space sampling of [Re(CO)3(Im)(Phen)]+ in aqueous solution.
• Comparison with conventional Wigner distribution and standard MD sampling techniques.

Main Results:

• The proposed protocols demonstrate advantages over Wigner and standard MD sampling, particularly for systems with anharmonic vibrations.
• The study highlights the limitations of regular Wigner and MD sampling in certain scenarios.
• The new methods offer improved accuracy in phase space exploration for complex molecular systems.

Conclusions:

• The developed "local temperature adjustment" and "individual QM/MM-based relaxation" protocols provide more reliable phase space sampling for chromophores.
• These methods are particularly beneficial when anharmonic vibrations preclude the use of Wigner sampling.
• The findings contribute to more accurate simulations of molecular optical and photophysical properties.