Efficient “On‐the‐Fly” calculation of Raman Spectra fromAb‐Initiomolecular dynamics: Application to hydrophobic/hydrophilic solutes in bulk water

Abstract

We present a novel computational method to accurately calculate Raman spectra from first principles. Together with an extension of the second-generation Car-Parrinello method of Kühne et al. (Phys. Rev. Lett. 2007, 98, 066401) to propagate maximally localized Wannier functions together with the nuclei, a speed-up of one order of magnitude can be observed. This scheme thus allows to routinely calculate finite-temperature Raman spectra "on-the-fly" by means of ab-initio molecular dynamics simulations. To demonstrate the predictive power of this approach we investigate the effect of hydrophobic and hydrophilic solutes in water solution on the infrared and Raman spectra.

Improved parameterization of the quantum harmonic oscillator model based on localized wannier functions to describe Van der Waals interactions in density functional theory

“…Interestingly, in a separate work where we devised a related method to compute Raman spectra based on MLWFs, [48] we determined that c 5 0.90, which is in a very good agreement with the aforementioned value by Silvestrelli. [31] As a consequence, in the present work we chose to keep c unchanged and only optimize the remaining two parameters, f and b.…”

“…Therefore, knowing the spreads S i of the MLWFs implies that the polarizabilities and characteristic frequencies can be directly computed, where γ are ζ are additional empirical parameters and Z i the atomic number . Equation is a consequence of the fact that α i is linearly related to the atomic volumes, and they had recently been employed to calculate finite temperature Raman spectra based on MLWFs …”

“…[45] Equation (5) is a consequence of the fact that a i is linearly related to the atomic volumes, [46] and they had recently been employed to calculate finite temperature Raman spectra based on MLWFs. [47,48] In the original parametrization of Silvestrelli and coworkers, [31,37] the three parameters a, b, and c, were determined so as to minimize the Mean Absolute Relative Error (MARE) with respect to quantum chemical reference calculations of the S22A test set. [49] Using the Perdew-Burke-Ernzerhof (PBE) XC functional as the Reference, [50] b 5 1.39, c 5 0.88 and f 5 1.30 is obtained.…”

Time‐dependent density functional theory study on direction‐dependent electron and hole transfer processes in molecular systems

“…Starting from these five configurations, new AIMD simulations were started including an extra electron, where the charge densities were calculated through diagonalization of the unconstrained (spin‐polarized) Kohn–Sham Hamiltonian. For the bond breaking criteria, we employed maximally localized Wannier functions (MLWFs) ,…”

“…For the bond breaking criteria, we employed maximally localized Wannier functions (MLWFs). [23] , [50][51][52] Structure of the bulk a-sulfur was adapted from Refs. [53][54][55].…”