Density functional theory in Firefly is implemented for restricted, unrestricted, and restricted-open wavefunctions. For each wavefunction, energies and analytical gradients are available. Analytical Hessians are currently not available. Instead, Hessians can be calculated in a semi-numerical fashion. Double hybrid functionals are an exception – for these functionals, only energies are currentl...

It is an understatement to say that the density functional theory (DFT) has strongly influenced the evolution of quantum chemistry during the past 15 years; the term “revolutionalized” is perhaps more appropriate. Based on the famous Hohenberg and Kohn theorems,1 DFT provided a sound basis for the development of computational strategies for obtaining information about the energetics, structure,...

Social interactions are characterized by distinct forms of interdependence, each of which has unique effects on how behavior unfolds within the interaction. Despite this, little is known about the psychological mechanisms that allow people to detect and respond to the nature of interdependence in any given interaction. We propose that interdependence theory provides clues regarding the structur...

We have investigated photosensitizing properties for porphrazine and eleven of its related derivatives based on time-dependent density functional theory (TD-DFT) calculations. The modles have been divided into two categories based on the existence of CN functional group in one category but not in the other one. The other functional groups include H, CH3, F, CF3, C6H5, and C6F5 counterparts. The...

Given a vector space of microscopic quantum observables, density functional theory is formulated on its dual space. A generalized Hohenberg-Kohn theorem and the existence of the universal energy functional in the dual space are proven. In this context ordinary density functional theory corresponds to the space of one-body multiplication operators. When the operators close under commutation to f...

Density functional theory (DFT) has become the most popular by far of the panoply of methods in quantum chemistry and the reason for this is simple. Where other schemes had become bogged down in mindnumbingly expensive and detailed treatments of the electron correlation problem, DFT simply shrugged, pointed at the Hohenberg–Kohn theorem, and asserted that the correlation energy can be written a...

A recent article in The Intelligencer described in some detail the theory of non-well-founded sets for the purpose of being able to solve freely equations of the sort X = A × X with A fixed ([Barwise & Moss, 1991]). Of course, the empty set is a solution, but what was wanted was a non-empty solution (in fact, the largest solution, if such exists). If X were a non-empty solution and x ∈ X, then ...