... P. Bultinck,* R. Vanholme, PLA Popelier, F. De Proft, § and P. Geerlings §. Department ... more ... P. Bultinck,* R. Vanholme, PLA Popelier, F. De Proft, § and P. Geerlings §. Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S-3), B-9000 Gent, Belgium, School of Chemistry, University ...
Molecular quantum similarity is evaluated for enantiomers in the case of molecules showing confor... more Molecular quantum similarity is evaluated for enantiomers in the case of molecules showing conformational flexibility, using our earlier proposed Boltzmann weighted similarity index. The conformers of the enantiomers of the amino acids alanine, asparagine, cysteine, leucine, serine, and valine were examined. Next to studying global indices, the evaluation of local similarity is carried out using our earlier proposed local similarity index based on the Hirshfeld partitioning, to further illustrate Mezey's holographic electron density theorem in chiral systems and to quantify dissimilarity of enantiomers.
Information-theory measures, in particular the Shannon entropy, Fisher information and statistica... more Information-theory measures, in particular the Shannon entropy, Fisher information and statistical complexity, are used to discuss the variations among several commonly encountered model two-electron correlated wavefunctions. The Hookean, Moshinsky, and three-parameter Chandrasekhar wavefunctions are considered in real and momentum space, with further comparisons to the Hookean–Hartree–Fock (HF) wavefunction of Ragot, the numerical HF limit, and the hydrogenic (pure Coulomb) limit. The purpose of the study is to quantitatively analyze the effect of different models for inclusion of electron–electron correlation on information-theoretical measures, including statistical complexity, which characterize the electron distribution in position and momentum space.
A hardness based similarity index for studying the quantum similarity for atoms is analyzed. The ... more A hardness based similarity index for studying the quantum similarity for atoms is analyzed. The investigation of hardness and Fukui functions of atoms leads to the construction of a quantum similarity measure, which can be interpreted as a quantified comparison of chemical reactivity of atoms. Evaluation of the new measure reveals periodic tendencies throughout Mendeleev’s table. Moreover on the diagonal the global hardness was recovered. Considering a corresponding quantum similarity index reveals that renormalization of the measure can mask periodic patterns. The hardness was calculated for atoms with nuclear charge 3⩽Z⩽103, using the best single configuration electron density functions available. Different hardness kernels were used and the importance of the different contributions to the kernel was investigated. The atomic self-similarities constructed in this way show a fair correlation with experimental atomic polarizability.
Many useful concepts developed within density functional theory provide much insight for the unde... more Many useful concepts developed within density functional theory provide much insight for the understanding and prediction of chemical reactivity, one of the main aims in the field of conceptual density functional theory. While approximate evaluations of such concepts exist, the analytical and efficient evaluation is, however, challenging, because such concepts are usually expressed in terms of functional derivatives with respect to the electron density, or partial derivatives with respect to the number of electrons, complicating the connection to the computational variables of the Kohn-Sham one-electron orbitals. Only recently, the analytical expressions for the chemical potential, one of the key concepts, have been derived by Cohen, Mori-Sánchez, and Yang, based on the potential functional theory formalism. In the present work, we obtain the analytical expressions for the real-space linear response function using the coupled perturbed Kohn-Sham and generalized Kohn-Sham equations,...
A density functional theory (DFT)-based method for the calculation of interaction energies in ads... more A density functional theory (DFT)-based method for the calculation of interaction energies in adsorption processes is proposed. The expression is based on the expansion of the energy of the adsorbed molecule with respect to the external potential perturbation introduced by adsorption in the zeolite cage. DFT interaction energies at the B3LYP/6-31G* level for the N2…Na+, Na+…CO and CO…Na+ systems in
The design of molecules with optimal properties is an important challenge in chemistry because of... more The design of molecules with optimal properties is an important challenge in chemistry because of the astronomically large number of possible stable structures that is accessible in chemical space. This obstacle can be overcome through inverse molecular design. In inverse design, one uses the computation of certain indices to design molecules with an optimal target property. In this study, for the first time, inverse design was used to optimize reactivity properties of molecules. Specifically, we optimized the acidity of substituted 2-naphthols, both in the ground and the excited state. Substituted 2-naphthols belong to the class of photoacids, showing enhanced acidity when excited from the singlet ground state to the first singlet excited state. The focus of this work is the ground state. As a measure of acidity, three different properties are optimized: the charge on the hydroxyl hydrogen atom of the acid, the charge on the negatively charged oxygen atom of the conjugate base and the energy difference between acid and conjugate base. Both the practical use of the methodology and the results for ground and excited states are discussed.
Bioelectrical impedance spectroscopy (BIS) can be a valuable tool in assessing changes in body co... more Bioelectrical impedance spectroscopy (BIS) can be a valuable tool in assessing changes in body composition. Although the validity of BIS in healthy subjects is relatively good, in patients considerably larger measurement errors have been reported. In this article the clinical usefulness of BIS in assessing nutritional status of one case study will be discussed. Interpretation of the predictions of BIS in this unstable patient was difficult. This is in agreement with the consensus that BIS does not give accurate prediction of body composition in individual patients. It is recommended that validation studies of BIS should focus on clinical aspects which can influence BIS measurements.
It is an understatement that Density Functional theory (DFT) played an important role in the deve... more It is an understatement that Density Functional theory (DFT) played an important role in the development of quantum chemistry in the past decade : it would be more correct to state that DFT revolutionarized quantum chemistry, offering a computational technique partly including electron correlation at a much better quality/cost ratio than the conventional post Hartree Fock (Moller Plesset, CI, Coupled Cluster …) wave function methods [1][2].
... P. Bultinck,* R. Vanholme, PLA Popelier, F. De Proft, § and P. Geerlings §. Department ... more ... P. Bultinck,* R. Vanholme, PLA Popelier, F. De Proft, § and P. Geerlings §. Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S-3), B-9000 Gent, Belgium, School of Chemistry, University ...
Molecular quantum similarity is evaluated for enantiomers in the case of molecules showing confor... more Molecular quantum similarity is evaluated for enantiomers in the case of molecules showing conformational flexibility, using our earlier proposed Boltzmann weighted similarity index. The conformers of the enantiomers of the amino acids alanine, asparagine, cysteine, leucine, serine, and valine were examined. Next to studying global indices, the evaluation of local similarity is carried out using our earlier proposed local similarity index based on the Hirshfeld partitioning, to further illustrate Mezey's holographic electron density theorem in chiral systems and to quantify dissimilarity of enantiomers.
Information-theory measures, in particular the Shannon entropy, Fisher information and statistica... more Information-theory measures, in particular the Shannon entropy, Fisher information and statistical complexity, are used to discuss the variations among several commonly encountered model two-electron correlated wavefunctions. The Hookean, Moshinsky, and three-parameter Chandrasekhar wavefunctions are considered in real and momentum space, with further comparisons to the Hookean–Hartree–Fock (HF) wavefunction of Ragot, the numerical HF limit, and the hydrogenic (pure Coulomb) limit. The purpose of the study is to quantitatively analyze the effect of different models for inclusion of electron–electron correlation on information-theoretical measures, including statistical complexity, which characterize the electron distribution in position and momentum space.
A hardness based similarity index for studying the quantum similarity for atoms is analyzed. The ... more A hardness based similarity index for studying the quantum similarity for atoms is analyzed. The investigation of hardness and Fukui functions of atoms leads to the construction of a quantum similarity measure, which can be interpreted as a quantified comparison of chemical reactivity of atoms. Evaluation of the new measure reveals periodic tendencies throughout Mendeleev’s table. Moreover on the diagonal the global hardness was recovered. Considering a corresponding quantum similarity index reveals that renormalization of the measure can mask periodic patterns. The hardness was calculated for atoms with nuclear charge 3⩽Z⩽103, using the best single configuration electron density functions available. Different hardness kernels were used and the importance of the different contributions to the kernel was investigated. The atomic self-similarities constructed in this way show a fair correlation with experimental atomic polarizability.
Many useful concepts developed within density functional theory provide much insight for the unde... more Many useful concepts developed within density functional theory provide much insight for the understanding and prediction of chemical reactivity, one of the main aims in the field of conceptual density functional theory. While approximate evaluations of such concepts exist, the analytical and efficient evaluation is, however, challenging, because such concepts are usually expressed in terms of functional derivatives with respect to the electron density, or partial derivatives with respect to the number of electrons, complicating the connection to the computational variables of the Kohn-Sham one-electron orbitals. Only recently, the analytical expressions for the chemical potential, one of the key concepts, have been derived by Cohen, Mori-Sánchez, and Yang, based on the potential functional theory formalism. In the present work, we obtain the analytical expressions for the real-space linear response function using the coupled perturbed Kohn-Sham and generalized Kohn-Sham equations,...
A density functional theory (DFT)-based method for the calculation of interaction energies in ads... more A density functional theory (DFT)-based method for the calculation of interaction energies in adsorption processes is proposed. The expression is based on the expansion of the energy of the adsorbed molecule with respect to the external potential perturbation introduced by adsorption in the zeolite cage. DFT interaction energies at the B3LYP/6-31G* level for the N2…Na+, Na+…CO and CO…Na+ systems in
The design of molecules with optimal properties is an important challenge in chemistry because of... more The design of molecules with optimal properties is an important challenge in chemistry because of the astronomically large number of possible stable structures that is accessible in chemical space. This obstacle can be overcome through inverse molecular design. In inverse design, one uses the computation of certain indices to design molecules with an optimal target property. In this study, for the first time, inverse design was used to optimize reactivity properties of molecules. Specifically, we optimized the acidity of substituted 2-naphthols, both in the ground and the excited state. Substituted 2-naphthols belong to the class of photoacids, showing enhanced acidity when excited from the singlet ground state to the first singlet excited state. The focus of this work is the ground state. As a measure of acidity, three different properties are optimized: the charge on the hydroxyl hydrogen atom of the acid, the charge on the negatively charged oxygen atom of the conjugate base and the energy difference between acid and conjugate base. Both the practical use of the methodology and the results for ground and excited states are discussed.
Bioelectrical impedance spectroscopy (BIS) can be a valuable tool in assessing changes in body co... more Bioelectrical impedance spectroscopy (BIS) can be a valuable tool in assessing changes in body composition. Although the validity of BIS in healthy subjects is relatively good, in patients considerably larger measurement errors have been reported. In this article the clinical usefulness of BIS in assessing nutritional status of one case study will be discussed. Interpretation of the predictions of BIS in this unstable patient was difficult. This is in agreement with the consensus that BIS does not give accurate prediction of body composition in individual patients. It is recommended that validation studies of BIS should focus on clinical aspects which can influence BIS measurements.
It is an understatement that Density Functional theory (DFT) played an important role in the deve... more It is an understatement that Density Functional theory (DFT) played an important role in the development of quantum chemistry in the past decade : it would be more correct to state that DFT revolutionarized quantum chemistry, offering a computational technique partly including electron correlation at a much better quality/cost ratio than the conventional post Hartree Fock (Moller Plesset, CI, Coupled Cluster …) wave function methods [1][2].
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