Time-dependent density functional methods for raman spectra in open-shell systems

Fredy W. Aquino, George C Schatz

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

We present an implementation of a time-dependent density functional theory (TD-DFT) linear response module in NWChem for unrestricted DFT calculations and apply it to the calculation of resonant Raman spectra in open-shell molecular systems using the short-time approximation. The new source code was validated and applied to simulate Raman spectra on several doublet organic radicals (e.g., benzyl, benzosemiquinone, TMPD, trans-stilbene anion and cation, and methyl viologen) and the metal complex copper phthalocyanine. We also introduce a divide-and-conquer approach for the evaluation of polarizabilities in relatively large systems (e.g., copper phthalocyanine). The implemented tool gives comparisons with experiment that are similar to what is commonly found for closed-shell systems, with good agreement for most features except for small frequency shifts, and occasionally large deviations for some modes that depend on the molecular system studied, experimental conditions not being accounted in the modeling such as solvation effects and extra solvent-based peaks, and approximations in the underlying theory. The approximations used in the quantum chemical modeling include (i) choice of exchange-correlation functional and basis set; (ii) harmonic approximation used in the frequency analysis to determine vibrational normal modes; and (iii) short-time approximation (omission of nuclear motion effects) used in calculating resonant Raman spectra.

Original languageEnglish
Pages (from-to)517-525
Number of pages9
JournalJournal of Physical Chemistry A
Volume118
Issue number2
DOIs
Publication statusPublished - Jan 16 2014

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Raman scattering
Raman spectra
approximation
Stilbenes
Paraquat
Coordination Complexes
Solvation
Discrete Fourier transforms
Density functional theory
Anions
Cations
copper
stilbene
frequency shift
solvation
modules
density functional theory
anions
deviation
harmonics

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Time-dependent density functional methods for raman spectra in open-shell systems. / Aquino, Fredy W.; Schatz, George C.

In: Journal of Physical Chemistry A, Vol. 118, No. 2, 16.01.2014, p. 517-525.

Research output: Contribution to journalArticle

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