Browsing by Author "Ziegler, Tom (deceased)"

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    Excited-State Studies with the Constricted Variational Density Functional Theory (CV-DF) Method
    (2016) Seidu, Issaka; Rauk, Arvi; Ziegler, Tom (deceased); Salahub, Dennis; MacCallum, Justin; Nooijen, Marcel; Sanders, Barry
    Theoretical calculations have played a vital role in understanding electronic properties of chemically and electronically relevant systems. Some of the roles played by theoretical approaches include the assignment and interpretation of spectra of chemical species such as the transition metal (TM) complexes. However, before these theoretical methods can be used as predictive tools in the chemical analysis of compounds for which experimental results are unavailable, the performance and scope of applicability of these methods must be well understood and improvements made wherever necessary. In this work, the Constricted Variational Density Functional Theory (CV-DFT) method is used in detailed analyses of excited-state properties of TM and other chemical species. Studies are carried out with the CV-DFT method in areas where the adiabatic Time-Dependent Density Functional Theory (ATD-DFT) method have been found insufficient, such as charge transfer (CT) and Rydberg excitations, as well as areas where ATD-DFT performed well. This was done to ensure that, the CV-DFT method not only show good performance for excitations poorly described by ATD-DFT but those that are sufficiently described as well. For a better understanding of the strengths and weaknesses of the CV-DFT methods, our calculated results are compared to experimental and/or high level ab initio results whenever available. Finally, an extension is made to CV-DFT for double excitation. These double excitations are known to be important for excited-state studies in conjugated systems such as the polyenes. Future work will be carried to examine the performance of this method. We find, in general, that CV-DFT shows accurate performance for excitations that are poorly described by the ATD-DFT method, and comparable performance for excitations in which ATD-DFT performs adequately.