Simulating Electronic Coherences Induced by Conical Intersections Using MASH: Application to Attosecond X-ray...

Area of Science:

• Quantum chemistry
• Computational chemistry
• Spectroscopy

Background:

• Nonadiabatic dynamics near conical intersections are crucial for understanding chemical reactions.
• Accurate prediction of electronic coherences is essential for interpreting spectroscopic data.
• Standard surface hopping methods sometimes struggle to precisely describe these coherences.

Purpose of the Study:

• To compare the Mapping Approach to Surface Hopping (MASH) with standard fewest-switches surface hopping.
• To evaluate the accuracy of MASH in predicting electronic coherences and nuclear dynamics.
• To assess the suitability of MASH for simulating novel X-ray spectroscopies.

Main Methods:

• Trajectory-based simulations were employed.
• The MASH method was compared against standard fewest-switches surface hopping.
• Three model systems with available full quantum-mechanical results were used for validation.

Main Results:

• MASH accurately captures electronic coherences, which standard surface hopping can fail to describe.
• Both methods showed comparable computational cost.
• Nuclear densities were also computed to assess method robustness.

Conclusions:

• MASH is a robust and accurate method for simulating nonadiabatic dynamics, particularly for electronic coherences.
• MASH offers a significant advantage over standard surface hopping for capturing quantum effects.
• MASH shows promise for applications in advanced spectroscopies like transient redistribution of ultrafast electronic coherences in attosecond Raman signals (TRUECARS).