Linear response properties of solvated systems: a computational study

Abstract

We present a computational study of static and dynamic linear polarizabilities in solution. We use different theoretical approaches to describe solvent effects, ranging from quantum mechanics/molecular mechanics (QM/MM) to quantum...

Time-Dependent Multilevel Density Functional Theory

“…Note that at this step, a part of the active–inactive polarization energy is introduced. Indeed, in previous works, we have shown that for neutral species, the largest part of the active–inactive polarization energy is taken into account by MLDFT. , Partitioning of the new density matrix into A and B densities by using a partial Cholesky decomposition for the active occupied orbitals. ,,,− The Cholesky decomposition of the total density D into D A and D B is unique if the same pivots are used. In this work, the Cholesky decomposition is performed by selecting the diagonal elements corresponding to the basis functions, which are centered on the active atoms: ,, D α β A = ∑ I J D α I D̃ I J − 1 D β J = ∑ I L α I L β I where I and J are the diagonal elements which are decomposed, D̃ is the submatrix of D containing the selected diagonals, and L αI are the Cholesky orbitals.…”

“…Partitioning of the new density matrix into A and B densities by using a partial Cholesky decomposition for the active occupied orbitals. ,,,− The Cholesky decomposition of the total density D into D A and D B is unique if the same pivots are used. In this work, the Cholesky decomposition is performed by selecting the diagonal elements corresponding to the basis functions, which are centered on the active atoms: ,, where I and J are the diagonal elements which are decomposed, D̃ is the submatrix of D containing the selected diagonals, and L αI are the Cholesky orbitals.…”

“…Similarly to its analogous ML Hartree–Fock (MLHF), − the MLDFT methodology restricts the molecular orbital (MO) space to that spanned by the active MOs only, providing a large computational saving compared to full DFT calculations. , In this work, we exploit this feature to extend the method to calculate electronic excitations using the time-dependent (TD) DFT formalism . To apply the method to real case systems, we couple MLDFT to a third classical MM layer, described using the polarizable fluctuating charge (FQ) force field, , which permits a proper description of long-range interactions at a reduced computational cost .…”

Continuum vs. atomistic approaches to computational spectroscopy of solvated systems

“…Indeed, molecular structure and response to external electromagnetic fields can be significantly altered by the environment, thus making the simulation for isolated systems mostly inappropriate for a reliable comparison with experimental findings. [13][14][15][16] Effective theoretical modeling of spectroscopy in the condensed phase requires catching the physico-chemical features of the simultaneous interaction of a chemical system with the environment and the external radiation field. 1,[17][18][19][20] Since spectroscopy arises from the interaction between the molecule and the radiation, which is in general driven by the electronic component, reliable modeling needs to resort to Quantum-Mechanical (QM) descriptions.…”

“…Indeed, molecular structure and response to external electromagnetic fields can be significantly altered by the environment, thus making the simulation for isolated systems mostly inappropriate for a reliable comparison with experimental findings. 13–16…”