Second-Order Mass-Weighting Scheme for Atom-Centered Density Matrix Propagation Molecular Dynamics.

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Molecular Dynamics

Background:

• Atom-centered density matrix propagation (ADMP) is an extended Lagrangian method for ab initio molecular dynamics.
• High adiabaticity between nuclear and electronic systems is crucial for Born-Oppenheimer (BO) surface accuracy.
• The fictitious electronic mass (μ) is a key parameter for optimizing electronic density propagation in ADMP.

Purpose of the Study:

• To develop a systematic procedure for determining the optimal fictitious electronic mass in ADMP.
• To improve the accuracy and efficiency of ab initio molecular dynamics simulations using ADMP.

Main Methods:

• Defined fictitious electronic normal modes by diagonalizing the electronic density matrix Hessian.
• Imposed a uniform frequency on these modes to calculate the optimal μ matrix.
• Employed Hessian-based mass-weighting in ADMP simulations with 0.1/0.2 fs time steps.

Main Results:

• Achieved high separation between nuclear and electronic frequencies, ensuring high adiabaticity.
• Demonstrated unprecedented accuracy in ADMP propagation.
• Obtained low errors in estimated nuclear vibrational frequencies.

Conclusions:

• The Hessian-based mass-weighting approach significantly advances ADMP accuracy.
• ADMP simulations become comparable to converged BO dynamics but with higher computational efficiency.
• This method offers a more rational approach to evaluating the fictitious electronic mass parameter in ADMP.