Origin-Independent Circular Dichroism Spectra for Molecular and Hybrid Systems with Real-Time Time-Dependent Density Functional Theory

We present a velocity gauge implementation for real-time time-dependent density functional theory (RT-TDDFT) calculations of electronic circular dichroism (ECD) spectra within the linear combination of atomic orbitals framework of the GPAW code. In contrast to the commonly used length gauge, which exhibits a pronounced dependence on the origin of the coordinate system, our velocity gauge implementation produces origin-independent ECD spectra already for moderately sized basis sets. The computational efficiency of the RT-TDDFT implementation in GPAW enables efficient ECD simulations of large finite systems, making chiroptical analyses of molecular and molecule–nanoparticle assemblies exceeding 1000 atoms feasible.