Excitation spectra of cubic perovskite titanates

2021 ◽  
Vol 32 ◽  
Author(s):  
Hieu Nguyen-Truong
Keyword(s):  
Density Functional Theory ◽  
Local Field ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Plasmon Mode ◽  
Time Dependent ◽  
Excitation Spectra ◽  
Functional Theory ◽  
Field Effects ◽  
Dependent Density

We calculate excitation spectra of cubic perovskites ATiO3 (A = Ca, Sr, Ba, Pb). The calculations are performed within the time-dependent density functional theory, including local field effects. The theoretical calculations show that the perovskites have a plasmon mode at around 12 eV, which is not observed in experiments.

Excitation Spectra in the Time-Dependent Density-Functional Theory with Gradient Correction

1999 ◽  
Vol 579 ◽  
Author(s):  
Naoto Uimezawa ◽  
Susumu Saito
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Local Density ◽  
Oscillator Strengths ◽  
Time Dependent ◽  
Basis Set ◽  
Excitation Spectra ◽  
Functional Theory ◽  
Gradient Correction ◽  
Dependent Density

ABSTRACTWe study tile optical absorption spectra of Na clusters using the time-dependent density-functional theory with gradient correction. A jellium-sphere background model, which is free from basis-set incompleteness error and is suitable for the comparison of various theoretical methods, is adopted. For energies of surface-plasinon excitations governing profiles of photoabsorption spectra with huge oscillator strengths., the gradient correction by van Leeiiwen and Baerends with correct asymptotic behavior of the effective potential is found to show considerable improvement over the time-dependent local-density approximation.

Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

2019 ◽  
Author(s):  
Kamal Batra ◽  
Stefan Zahn ◽  
Thomas Heine
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Absolute Error ◽  
Time Dependent ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
Framework Materials ◽  
Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

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