A Density Functional Theory and Semiempirical Framework for Trajectory Surface Hopping on Extended Systems

Nonadiabatic molecular dynamics simulations provide a
theoretical
understanding of various excited-state processes in photochemistry,
offering access to band widths, radiative or nonradiative relaxation
and corresponding lifetimes, excited-state energies, and charge transfer.
The range of method developments within the framework of time-dependent
density functional theory is exceedingly large for molecular quantum
chemistry. Still, it shrinks significantly when aiming to treat periodic
boundary conditions. To address this gap and complement existing software
packages for solid-state nonadiabatic molecular dynamics, we present
an interface between the CP2K electronic structure and the NEWTON-X
surface hopping codes. The interface features the generation of initial
conditions, as well as adiabatic and nonadiabatic molecular dynamics,
based on phenomenological or numerical time-derivative couplings.
Setups are validated on gas-phase pyrazine, with electronic absorption
spectra and excited-state populations for transitions between the
lowest singlet states being in agreement with established molecular
quantum chemistry methods. Extending the system size to crystalline
pyrazine, limitations of approximate couplings are discussed, and
the efficiency and applicability of the interface are demonstrated
by computing broad spectra over several eV and 100 fs trajectories,
considering couplings between all 80th lowest excited states, at low
computational cost with a mixed semiempirical density functional theory
setup.

非绝热分子动力学（Nonadiabatic molecular dynamics）模拟可为光化学中的各类激发态过程提供理论认知，可用于获取能带宽度、辐射/非辐射弛豫及其对应寿命、激发态能量以及电荷转移等信息。在分子量子化学领域，含时密度泛函理论（time-dependent density functional theory）框架下的方法开发范畴极为庞大，但当目标为处理周期性边界条件（periodic boundary conditions）时，该范畴会显著收窄。为填补这一空白并完善现有的固态非绝热分子动力学软件套件，我们开发了CP2K电子结构程序与NEWTON-X表面跳跃（surface hopping）代码间的接口。该接口可基于现象学或数值时间导数耦合，实现初始条件生成以及绝热与非绝热分子动力学模拟。我们通过气相吡嗪体系对该接口的参数设置进行验证，结果显示，最低单重态间跃迁的电子吸收光谱与激发态布居，与已成熟的分子量子化学方法结果一致。当将体系规模拓展至晶态吡嗪时，我们讨论了近似耦合方法的局限性，并通过混合半经验密度泛函理论设置，以较低计算成本计算了跨越数个电子伏特的宽谱以及100飞秒级别的动力学轨迹，同时考虑了前80个最低激发态间的耦合，由此验证了该接口的效率与适用性。