Density functional theory molecular properties

K. Aidas, K.V. Mikkelsen, J. Kongsted, Modelling spectroscopic properties of large molecular systems, the combined density functional theory/molecular mechanics approach, J. Chem. Meth. Sci. Eng. 7 (2007) 135. 

Several different kinds of quantum-chemical descriptors have been defined, and these can be broadly divided into energy-based descriptors, local quantum-chemical properties, descriptors based on the Density Functional Theory, molecular orbital energies, superdelocalizability indices, frontier orbital electron densities, and polarizabilities [Cartier and Rivail, 1987 Bergmann and Hinze, 1996 Karelson et al, 1996]. 

K. Aidas, K. V. Mikkelsen and J. Kongsted, Modelling Spectroscopic Properties of Large Molecular Systems. The Combined Density Functional Theory/Molecular Mechanics Approach , J. Comput. Methods Sci. Eng., 2007, 7, 135. 

In 1985 Car and Parrinello invented a method [111-113] in which molecular dynamics (MD) methods are combined with first-principles computations such that the interatomic forces due to the electronic degrees of freedom are computed by density functional theory [114-116] and the statistical properties by the MD method. This method and related ab initio simulations have been successfully applied to carbon [117], silicon [118-120], copper [121], surface reconstruction [122-128], atomic clusters [129-133], molecular crystals [134], the epitaxial growth of metals [135-140], and many other systems for a review see Ref. 113. 

Ab initio molecular orbital theory is concerned with predicting the properties of atomic and molecular systems. It is based upon the fundamental laws of quantum mechanics and uses a variety of mathematical transformation and approximation techniques to solve the fundamental equations. This appendix provides an introductory overview of the theory underlying ab initio electronic structure methods. The final section provides a similar overview of the theory underlying Density Functional Theory methods. 

Chattaraj PK, Parr RG (1993) Density Functional Theory of Chemical Hardness. 80 11-26 Cheh AM, Neilands JP (1976) The j -Aminoevulinate Dehydratases Molecular and Environmental Properties. 29 123-169 Chimiak A, Neilands JB (1984) Lysine Analogues of Siderophores. 58 89-96 Christensen JJ, see Izatt RM (1973) 16 161-189... 

The molecular interpretation of major topics in catalytic kinetics will be highlighted based on insights on the properties of transition-state intermediates as deduced from computational chemical density functional theory (DFT) calculations. 

Thus, the electron density already provides all the ingredients that we identified as being necessary for setting up the system specific Hamiltonian and it seems at least very plausible that in fact p( ) suffices for a complete determination of all molecular properties (of course, this does not relieve us from the task of actually solving the corresponding Schrodinger equation and all the difficulties related to this). As noted by Handy, 1994, these very simple and beautifully intuitive arguments in favor of density functional theory are attributed to E. B. Wilson. So the answer to the question posed in the caption to this section is certainly a loud and clear Yes . 

Geerhngs, P., De Proft, F., Martin, J. M. L., 1996, Density Functional Theory Concepts and Techniques for Studying Molecular Charge Distributions and Related Properties , in Recent Developments and Applications of Modem Density Functional, Seminario, J. M. (ed.), Elsevier, Amsterdam. 

Scheiner, A. C., Baker, J., Andzelm, J. W., 1997, Molecular Energies and Properties from Density Functional Theory Exploring Basis Set Dependence of Kohn-Sham Equation Using Several Density Functionals , J. Comput. 

The electron density of a non-degenerate ground state system determines essentially all physical properties of the system. This statement of the Hohenberg-Kohn theorem of Density Functional Theory plays an exceptionally important role among all the fundamental relations of Molecular Physics. 

In a rigorous sense, non-transferability of molecular parts has profound implications on chemical conclusions based on electron densities. Since some of the original results on the utility and reliability of transferred electron densities have been derived within the framework of density functional theory, here we shall follow this approach, and describe a recent result on a general, holographic property of electron density fragments of complete, boundaryless molecular electron densities. 

Bakalarski, G., P. Grochowski, J. S. Kwiatkowski, B. Lesyng, and J. Leszczynski. 1996. Molecular and electrostatic properties of the N-methylated nucleic acid bases by density functional theory. Chem. Phys. 204, 301. 

Of course, experimental methods are used to determine the molecular properties of 1,2,4-triazoles but computational studies, particularly density functional theory (DFT) calculations, are frequently carried out to predict and confirm the experimental findings. Calculation of the fundamental vibrational frequencies using the 6-311G(d,p) basis set has been used to support a comprehensive study of the vibrational spectra of 1,2,4-triazole <2000JST(530)183>. 

AMI semi-empirical and B3LYP/6-31G(d)/AMl density functional theory (DFT) computational studies were performed with the purpose of determining which variously substituted 1,3,4-oxadiazoles would participate in Diels-Alder reactions as dienes and under what conditions. Also, bond orders for 1,3,4-oxadiazole and its 2,5-diacetyl, 2,5-dimethyl, 2,5-di(trifluoromethyl), and 2,5-di(methoxycarbonyl) derivatives were calculated <1998JMT153>. The AMI method was also used to evaluate the electronic properties of 2,5-bis[5-(4,5,6,7-tetrahydrobenzo[A thien-2-yl)thien-2-yl]-l,3,4-oxadiazole 8. The experimentally determined redox potentials were compared with the calculated highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) energies. The performance of the available parameters from AMI was verified with other semi-empirical calculations (PM3, MNDO) as well as by ab initio methods <1998CEJ2211>. 

Ab-initio CAChe features all of the above plus ab-initio and density functional methods. This program requires a workstation (Windows NT minimum or SGI and IBM unix-based machines) and can be used to build and visualize results from ab-initio programs (e.g., Gaussian, see description under Gaussian, Inc.). Also, CAChe directly interfaces to Dgauss , a computational chemistry package that uses density functional theory to predict molecular structures, properties, and energetics. 

---