Density functional theory selected application

Veillard is not convinced that ab initio Hartree-Fock theory will ever lead to the kind of black box calculations now possible for some organic molecules. Tsipis is rather more positive recognising the possibilities for a complementary interplay between theory and experiment but is nevertheless of the opinion that there exists no general canon for the efficacious selection and application of the most eligible computational method for the study of a certain compound or series of compounds . This view does not appear to be shared by Ziegler or Comba who convey quite positive messages concerning the capabilities of Density Functional Theory and Molecular Mechanics respectively. 

The present review has been very selective, stressing the rationale behind density-functional methods above their applications and excluding many important topics (both theoretical and computational). The interested reader may refer to anyone of the many books [91-93] or review articles [94-101] on density-functional theory for more details. Of special importance is the extension of density-functional theory to time-dependent external potentials [102-105], as this enables the dynamical behavior of molecules, including electronic excitation, to be addressed in the context of DFT [106-108]. As they are particularly relevant to the present discussion, we cite several articles related to the formal foundations of density-functional theory [85,100,109-111], linear-scaling methods [63,112-116], exchange-correlation energy functionals [25, 117-122], and qualitative tools for describing chemical reactions [123-126,126-132]. 

In spite of the advent of density functional theory (see Section 21.2), the number of publications with semiempirical calculations remains high. In the Science Citation Index, one finds for each of the past ten years more than 1000 such papers under the topic semiempirical/MNDO/AMl/PM3 , the actual numbers fluctuating between 1100 and 1500 (1994-2003) this should be regarded as a lower limit of the actual usage, for obvious reasons. Since DFT calculations have replaced semiempirical calculations in many studies on medium-sized molecules, the latter must have found new areas of application. In this section, we attempt to identify such areas from a survey of the recent literature. Given the diverse activities in this field, it is clear this cannot be a comprehensive overview and that the selection of topics will necessarily be subjective. 

Abstract Density functional theory (DFT) in various modifications provides the basis for studying the electronic structure of solids and surfaces by means of our WIEN2k code, which is based on the augmented plane wave (APW) method. Several properties, which can be obtained with this code, are summarized and the application of the code is illustrated with four selected examples focusing on very different aspects from electron-structure relations, complex surfaces or disordered layer compounds to the dependence of the equilibrium lattice constants on the DFT functionals. 

The applications are so many that it is difficult to select a few. Limiting the attention to some basic issues, one may mention a recent study using density functional theory and molecular orbital G3(MP2) method to provide thermodynamic data for the analysis of the photochemistry of ketones on Ti02. The bond energies of a range of gem-diols, RR C(OH)2, have been used as models for the binding to the titania surface (see Scheme 24). ... 

In 1985, Car and Parrinello published a seminal article on an Unified approach for molecular dynamics and density functional theory Phys. Rev. Lett. 5S (1985) 2471). This paper established a basis for parameter-firee molecular dynamics simulations in which all the interactions are calculated on the fly via a first-principles quantum mechanical method. In the 15 years of its existence, the Car-Parrinello method has found widespread applications that expanded rapidly from physics to chemistry and, most recently, even into biology. In this article, the foundations of the method in its most common implementation, the one based on density functional theory, plane wave basis sets and pseudopotentials are described and extensions to the original scheme are outlined. The current power of Car-Parrinello simulations is illustrated by presenting selected case studies and possible future directions are sketched in the final outlook. 

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