5th SmoleQ Greeting Seminar (2025.02.18 at 17:00 (JST))

 

Speaker: 

Ravi Kumar

Title: 

Atomic-orbital-Based linear response theory for Molecular Spectroscopy.

Abstract:

Molecular spectroscopic techniques, including Raman, Infrared (IR), and Vibrational Circular Dichroism (VCD), are powerful tools for molecular and material characterization. The analytical calculation of these spectra using molecular orbital (MO)-based response theory has been implemented within the Kohn-Sham DFT framework in CP2K code [1–3]. However, MO-based methods exhibit cubic scaling with system size, which limits their applicability to large systems. To address this limitation, we implemented an atomic orbital (AO)- based linear response theory [4, 5], which enables linear-scaling computation of these response properties. We employ the optimization of one-electron density matrix and energy using exponential parametrization scheme introduced by Helgaker et al. [6, 7]. The AO-based response solver produces Raman, IR and VCD spectra that are consistent with those from MO-based methods, validating its accuracy.

References:

[1] Sandra Luber, Marcella Iannuzzi, and Jürg Hutter, “Raman spectra from ab initio molecular dynamics and its application

to liquid S-methyloxirane,” J. Chem. Phys. 141, 094503 (2014).

[2] Edward Ditler, Chandan Kumar, and Sandra Luber, “Analytic calculation and analysis of atomic polar tensors for molecules

and materials using the gaussian and plane waves approach,” The Journal of Chemical Physics 154, 104121 (2021).

[3] Edward Ditler, Tomáš Zimmermann, Chandan Kumar, and Sandra Luber, “Implementation of nuclear velocity perturbation

and magnetic field perturbation theory in cp2k and their application to vibrational circular dichroism,” Journal of Chemical

Theory and Computation 18, 2448–2461 (2022).

[4] Ravi Kumar and Sandra Lubar, “Electric Dipole Polarizability Calculation for Periodic and Non-periodic Systems using

Atomic-Orbitals-based Linear Response Theory,” (submitted).

[5] Ravi Kumar and Sandra Lubar, “Calculation of vibrational circular dichroism spectra employing nuclear velocity perturbation

or magnetic field perturbation theory using atomic-orbital-based linear response approach,” (submitted).

[6] Trygve Helgaker, Helena Larsen, Jeppe Olsen, and Poul Jorgensen, “Direct optimization of the ao density matrix in

hartree-fock and kohn-sham theories,” Chemical Physics Letters 327, 397–403 (2000).

[7] Helena Larsen, Trygve Helgaker, Jeppe Olsen, and Poul Jørgensen, “Geometrical derivatives and magnetic properties