Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a ...Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a series of proton donors of different acidic strength, i.e. water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol, pentachlorophenol, picric acid and hydrogen chlordide. Computed H-bond interaction energies (ΔEc), internuclear and intermolecular distances r(O…H) and r(O…O), infrared frequency shifts Δv(C=O) and (Δv(OH) are proved to be reliable parameters for predicting the preferred interaction site of 3-methyl-4-pyrimidone. These computational data suggest that the O-H…O=C complex is preferred with water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol and pentachlorophenol. However, for H-bonding with stronger acids such as picric acid or hydrochloric acid, the computational data suggest that the H-bonding occurs at the N1 ring atom of 3-methyl-4-pyrimidone. In the O-H…O=C com- plex, where the H-bond at the carbonyl O-atom can be oriented “anti” (Ha) and “syn” (Hb) with respect to the N3 atom, the same computational data suggest a higher stability of the “anti-O” compared to the “syn-O” orientation.展开更多
The energy band-gap and related factors of tantalum pentoxide with hexagonal phase were investigated using hybrid functional B3LYP and sX-LDA methods. The results showed that both sX-LDA and B3LYP techniques reveal th...The energy band-gap and related factors of tantalum pentoxide with hexagonal phase were investigated using hybrid functional B3LYP and sX-LDA methods. The results showed that both sX-LDA and B3LYP techniques reveal the indirect semiconductor nature of δ-Ta2O5, whereas the obtained value of energy band-gap is much higher than previous theoretical reports but closer to the experimental data. The optical band- gap of δ-Ta2O5 is expected to originate from the O 2p→Ta 5d transition which may benefit from the d-s-p hybridization.展开更多
Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be int...Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be intrinsically captured by the(semi)-local ingredients and the exact-exchange used in the popular hybrid DFAs.Overemphasizing the accuracy on the equilibrium region for the functional construction would likely deteriorate the overall performance on the other regions of potential energy surfaces.In consequence,the empirical dispersion correction becomes the standard component in DFAs to treat the non-bonded interactions.In this Letter,we demonstrate that without the use of empirical dispersion correction,doubly hybrid approximations,in particular two recently proposed rev XYG3 and XYG7 functionals,hold the promise to have a balanced description of non-bonded interactions on the whole potential energy curves for several prototypes ofπ-π,CH/π,and SH/πinteractions.The error of rev XYG3 and XYG7 for non-bonded interactions is around 0.1 kcal/mol,and their potential energy curves almost coincide with the accurate CCSD(T)/CBS curves.展开更多
文摘Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a series of proton donors of different acidic strength, i.e. water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol, pentachlorophenol, picric acid and hydrogen chlordide. Computed H-bond interaction energies (ΔEc), internuclear and intermolecular distances r(O…H) and r(O…O), infrared frequency shifts Δv(C=O) and (Δv(OH) are proved to be reliable parameters for predicting the preferred interaction site of 3-methyl-4-pyrimidone. These computational data suggest that the O-H…O=C complex is preferred with water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol and pentachlorophenol. However, for H-bonding with stronger acids such as picric acid or hydrochloric acid, the computational data suggest that the H-bonding occurs at the N1 ring atom of 3-methyl-4-pyrimidone. In the O-H…O=C com- plex, where the H-bond at the carbonyl O-atom can be oriented “anti” (Ha) and “syn” (Hb) with respect to the N3 atom, the same computational data suggest a higher stability of the “anti-O” compared to the “syn-O” orientation.
基金Funded by the National Natural Science Foundation of China(No.51102172)Hebei Natural Science Foundation(No.E2013210038)+1 种基金Colleges and Universities in Hebei Province Science and Technology Research Project(No.YQ2014033)Hebei Key Discipline Construction Project
文摘The energy band-gap and related factors of tantalum pentoxide with hexagonal phase were investigated using hybrid functional B3LYP and sX-LDA methods. The results showed that both sX-LDA and B3LYP techniques reveal the indirect semiconductor nature of δ-Ta2O5, whereas the obtained value of energy band-gap is much higher than previous theoretical reports but closer to the experimental data. The optical band- gap of δ-Ta2O5 is expected to originate from the O 2p→Ta 5d transition which may benefit from the d-s-p hybridization.
基金supported by the National Natural Science Foundation of China(No.21973015,No.22125301,No.91427301)the Science Challenge Project(TZ2018004)+1 种基金Innovative Research Team of High-Level Local universities in Shanghaia Key Laboratory Program of the Education Commission of Shanghai Municipality(ZDSYS14005)。
文摘Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be intrinsically captured by the(semi)-local ingredients and the exact-exchange used in the popular hybrid DFAs.Overemphasizing the accuracy on the equilibrium region for the functional construction would likely deteriorate the overall performance on the other regions of potential energy surfaces.In consequence,the empirical dispersion correction becomes the standard component in DFAs to treat the non-bonded interactions.In this Letter,we demonstrate that without the use of empirical dispersion correction,doubly hybrid approximations,in particular two recently proposed rev XYG3 and XYG7 functionals,hold the promise to have a balanced description of non-bonded interactions on the whole potential energy curves for several prototypes ofπ-π,CH/π,and SH/πinteractions.The error of rev XYG3 and XYG7 for non-bonded interactions is around 0.1 kcal/mol,and their potential energy curves almost coincide with the accurate CCSD(T)/CBS curves.
