The Experts below are selected from a list of 20562 Experts worldwide ranked by ideXlab platform
Wei-hai Fang - One of the best experts on this subject based on the ideXlab platform.
-
photodecarbonylation mechanism of cyclopropenone in the gas phase Electronic Structure Calculation and aims dynamics simulation
Journal of Physical Chemistry A, 2014Co-Authors: Lihong Liu, Shu-hua Xia, Wei-hai FangAbstract:In this article, Structures and energies of cyclopropenone in the low-lying Electronic states have been determined by the CASSCF and MS-CASPT2 Calculations with different basis sets. Two minimum-energy conical intersections (CI-1 and CI-2) between S0 and S1 were obtained and their topographic characters were characterized by the SA4-CAS(10,9) calculated energy gradients and nonadiabatic coupling vectors. The AIMS method was used to carry out nonadiabatic dynamics simulation with ab initio Calculation performed at the SA4-CAS(10,9) level. On the basis of time evolution of wave functions simulated here, the S1 lifetime is fitted to be 125 fs with a pure exponential decay for the S1 Electronic population. The CI-1 intersection is mainly responsible for ultrafast S1→S0 nonadiabatic transition and the photoinduced decarbonylation is a sequential process, where the first C—C bond is broken in the S1 state and fission of the second C—C bond occurs in the S0 state as a result of the S1→S0 internal conversion via ...
-
Photodecarbonylation Mechanism of Cyclopropenone in the Gas Phase: Electronic Structure Calculation and AIMS Dynamics Simulation
2014Co-Authors: Lihong Liu, Shu-hua Xia, Wei-hai FangAbstract:In this article, Structures and energies of cyclopropenone in the low-lying Electronic states have been determined by the CASSCF and MS-CASPT2 Calculations with different basis sets. Two minimum-energy conical intersections (CI-1 and CI-2) between S0 and S1 were obtained and their topographic characters were characterized by the SA4-CAS(10,9) calculated energy gradients and nonadiabatic coupling vectors. The AIMS method was used to carry out nonadiabatic dynamics simulation with ab initio Calculation performed at the SA4-CAS(10,9) level. On the basis of time evolution of wave functions simulated here, the S1 lifetime is fitted to be 125 fs with a pure exponential decay for the S1 Electronic population. The CI-1 intersection is mainly responsible for ultrafast S1→S0 nonadiabatic transition and the photoinduced decarbonylation is a sequential process, where the first CC bond is broken in the S1 state and fission of the second CC bond occurs in the S0 state as a result of the S1→S0 internal conversion via the CI-1 region. As a minor channel through the CI-2 region, the decarbonylation proceeds in an asynchronous concerted way. Effects of the S1 excess energies and the S1–S0 energy gap on the nonadiabatic dynamics were examined, which reveals that the S1→S0 nonadiabatic transition occurs within a small energy gap and high-energy conical intersection regions can play an important role. The present study provides new insights into mechanistic photochemistry of cyclopropenones and reveals that the AIMS dynamics simulation at a high-accuracy ab initio level is a powerful tool for exploring a mechanism of an ultrafast photochemical reaction
-
insights into mechanistic photodissociation of chloroacetone from a combination of Electronic Structure Calculation and molecular dynamics simulation
Journal of Chemical Physics, 2011Co-Authors: Lin Shen, Lihong Liu, Jun Cao, Wei-hai FangAbstract:The stationary and intersection Structures on the S0 and S1 potential energy surfaces of CH3COCH2Cl have been determined by the CAS(10,8)/cc-pVDZ optimizations and their relative energies are refined by the CASPT2//CAS(10,8)/cc-pVDZ single-point Calculations. Non-adiabatic molecular dynamics simulations were performed on the basis of the state-averaged CAS(10,8)/cc-pVDZ calculated energies, energy gradients, and Hessian matrix for the S0 and S1 states. It is found that the features of the S1 potential energy surface and non-adiabatic effect control the selectivity of the two α-C–C bond fissions, which provides a reasonable explanation why one α-C–C bond was observed as a primary channel and the other is ruled out even if CH3COCH2Cl is excited at 193 nm. The β-C–Cl fission is determined to be a dominant channel once the CH3COCH2Cl molecule is excited to the S1 state and the β-C–Cl:α-C–C branching ratio is estimated by the RRKM rate theory to be 15:1 at 193 nm, which is overestimated in comparison with the ...
Lihong Liu - One of the best experts on this subject based on the ideXlab platform.
-
photodecarbonylation mechanism of cyclopropenone in the gas phase Electronic Structure Calculation and aims dynamics simulation
Journal of Physical Chemistry A, 2014Co-Authors: Lihong Liu, Shu-hua Xia, Wei-hai FangAbstract:In this article, Structures and energies of cyclopropenone in the low-lying Electronic states have been determined by the CASSCF and MS-CASPT2 Calculations with different basis sets. Two minimum-energy conical intersections (CI-1 and CI-2) between S0 and S1 were obtained and their topographic characters were characterized by the SA4-CAS(10,9) calculated energy gradients and nonadiabatic coupling vectors. The AIMS method was used to carry out nonadiabatic dynamics simulation with ab initio Calculation performed at the SA4-CAS(10,9) level. On the basis of time evolution of wave functions simulated here, the S1 lifetime is fitted to be 125 fs with a pure exponential decay for the S1 Electronic population. The CI-1 intersection is mainly responsible for ultrafast S1→S0 nonadiabatic transition and the photoinduced decarbonylation is a sequential process, where the first C—C bond is broken in the S1 state and fission of the second C—C bond occurs in the S0 state as a result of the S1→S0 internal conversion via ...
-
Photodecarbonylation Mechanism of Cyclopropenone in the Gas Phase: Electronic Structure Calculation and AIMS Dynamics Simulation
2014Co-Authors: Lihong Liu, Shu-hua Xia, Wei-hai FangAbstract:In this article, Structures and energies of cyclopropenone in the low-lying Electronic states have been determined by the CASSCF and MS-CASPT2 Calculations with different basis sets. Two minimum-energy conical intersections (CI-1 and CI-2) between S0 and S1 were obtained and their topographic characters were characterized by the SA4-CAS(10,9) calculated energy gradients and nonadiabatic coupling vectors. The AIMS method was used to carry out nonadiabatic dynamics simulation with ab initio Calculation performed at the SA4-CAS(10,9) level. On the basis of time evolution of wave functions simulated here, the S1 lifetime is fitted to be 125 fs with a pure exponential decay for the S1 Electronic population. The CI-1 intersection is mainly responsible for ultrafast S1→S0 nonadiabatic transition and the photoinduced decarbonylation is a sequential process, where the first CC bond is broken in the S1 state and fission of the second CC bond occurs in the S0 state as a result of the S1→S0 internal conversion via the CI-1 region. As a minor channel through the CI-2 region, the decarbonylation proceeds in an asynchronous concerted way. Effects of the S1 excess energies and the S1–S0 energy gap on the nonadiabatic dynamics were examined, which reveals that the S1→S0 nonadiabatic transition occurs within a small energy gap and high-energy conical intersection regions can play an important role. The present study provides new insights into mechanistic photochemistry of cyclopropenones and reveals that the AIMS dynamics simulation at a high-accuracy ab initio level is a powerful tool for exploring a mechanism of an ultrafast photochemical reaction
-
insights into mechanistic photodissociation of chloroacetone from a combination of Electronic Structure Calculation and molecular dynamics simulation
Journal of Chemical Physics, 2011Co-Authors: Lin Shen, Lihong Liu, Jun Cao, Wei-hai FangAbstract:The stationary and intersection Structures on the S0 and S1 potential energy surfaces of CH3COCH2Cl have been determined by the CAS(10,8)/cc-pVDZ optimizations and their relative energies are refined by the CASPT2//CAS(10,8)/cc-pVDZ single-point Calculations. Non-adiabatic molecular dynamics simulations were performed on the basis of the state-averaged CAS(10,8)/cc-pVDZ calculated energies, energy gradients, and Hessian matrix for the S0 and S1 states. It is found that the features of the S1 potential energy surface and non-adiabatic effect control the selectivity of the two α-C–C bond fissions, which provides a reasonable explanation why one α-C–C bond was observed as a primary channel and the other is ruled out even if CH3COCH2Cl is excited at 193 nm. The β-C–Cl fission is determined to be a dominant channel once the CH3COCH2Cl molecule is excited to the S1 state and the β-C–Cl:α-C–C branching ratio is estimated by the RRKM rate theory to be 15:1 at 193 nm, which is overestimated in comparison with the ...
Constantinos C Stoumpos - One of the best experts on this subject based on the ideXlab platform.
-
synthesis Structure and Electronic Structure Calculation of a new centrosymmetric borate pb2o bo2 oh based on anion centered opb4 tetrahedra
ChemInform, 2016Co-Authors: Feng Sun, Li Wang, Constantinos C StoumposAbstract:The new title compound is prepared by hydrothermal reaction of a 1:2:5 molar mixture of Pb(NO3)2, SrCO3, and H3BO3 in 1 M KOH (autoclave, 180 °C, 1 d, 40% yield).
-
synthesis Structure and Electronic Structure Calculation of a new centrosymmetric borate pb2o bo2 oh based on anion centered opb4 tetrahedra
Journal of Solid State Chemistry, 2016Co-Authors: Feng Sun, Li Wang, Constantinos C StoumposAbstract:Abstract The synthesis, Structure, and characterization of a new centrosymmetric borate Pb 2 O[BO 2 (OH)] based on anion-centered OPb 4 tetrahedra are reported. Pb 2 O[BO 2 (OH)] crystallizes in monoclinic space group C2/m with a =12.725(7) A, b =5.698(3) A, c =7.344(4) A, β =116.277(6)°. The Electronic band Structure and density of states of Pb 2 O[BO 2 (OH)] have been calculated via the density functional theory (DFT). Electron density difference Calculation indicates that lone-pair electrons of Pb 2+ cation should be stereoactive.
Myung Joon Han - One of the best experts on this subject based on the ideXlab platform.
-
calculating branching ratio and spin orbit coupling from first principles a formalism and its application to iridates
Physical Review B, 2016Co-Authors: Jaehoon Sim, Hongkee Yoon, Sang Hyeon Park, Myung Joon HanAbstract:We present a simple technique to calculate spin-orbit coupling, $\ensuremath{\langle}\mathbf{L}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{S}\ensuremath{\rangle}$, and branching ratio measured in x-ray absorption spectroscopy. Our method is for first-principles Electronic Structure Calculation, and its implementation is straightforward for any of the standard formulations and codes. We applied this technique to several different large spin-orbit coupling iridates. The calculated $\ensuremath{\langle}\mathbf{L}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{S}\ensuremath{\rangle}$ and branching ratio of a prototype ${j}_{\mathrm{eff}}=1/2$ Mott insulator, ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$, are in good agreement with recent experimental data over the wide range of Rh doping. Three different double-perovskite iridates (namely, ${\mathrm{Sr}}_{2}{\mathrm{MgIrO}}_{6}, {\mathrm{Sr}}_{2}{\mathrm{ScIrO}}_{6}$, and ${\mathrm{Sr}}_{2}{\mathrm{TiIrO}}_{6}$) are also well described. This technique can serve as a promising tool for studying large spin-orbit coupling materials from first principles and for understanding experiments.
-
o n lda u Electronic Structure Calculation method based on the nonorthogonal pseudoatomic orbital basis
Physical Review B, 2006Co-Authors: Myung Joon Han, Taisuke OzakiAbstract:We report an implementation of the $\mathrm{LDA}+U$ method based on the state-of-the-art linear combination of pseudo-atomic orbital (LCPAO) method, which is suitable for large-scale $\mathrm{O}(N)$ Electronic Structure Calculations based on the density functional theory. By introducing a dual representation of the occupation number matrix instead of the on-site or full representations, the $\mathrm{LDA}+U$ formalism is refined to be consistent with a nonorthogonal LCPAO basis in regard to the sum rule of the total number of electrons. For typical transition metal oxide bulk systems, the band gap, magnetic moment, and detailed Electronic Structures are investigated with the different choices of basis orbitals and effective $U$ values as well as the definition of the occupation number matrix. The results are in good agreement with previous theoretical and experimental studies, indicating that the proposed $\mathrm{LDA}+U$ scheme combined with the $\mathrm{O}(N)$ method is a quite promising approach for the study of large-scale correlated material systems consisting of localized electrons. We discuss the Electronic Structure and magnetic properties of ${(\mathrm{Ni}\mathrm{O})}_{m}∕{(\mathrm{Co}\mathrm{O})}_{n}$ superlattices as an application of our method.
Tapas Chakraborty - One of the best experts on this subject based on the ideXlab platform.
-
ch o interaction lowers hydrogen transfer barrier to keto enol tautomerization of β cyclohexanedione combined infrared spectroscopic and Electronic Structure Calculation study
Journal of Physical Chemistry A, 2012Co-Authors: Biman Bandyopadhyay, Prasenjit Pandey, Pujarini Banerjee, Amit K Samanta, Tapas ChakrabortyAbstract:Molecular association and keto–enol tautomerization of β-cyclohexanedione (β-CHD) have been investigated in argon matrix and also in a thin solid film prepared by depositing pure β-CHD vapor on a cold (8 K) KBr window. Infrared spectra reveal that, in low-pressure vapor and argon matrix, the molecules are exclusively in diketo tautomeric form. The CH···O hydrogen bonded dimers of the diketo tautomer are produced by annealing the matrix at 28 K. No indication is found for keto–enol tautomerization of β-CHD in dimeric complexes in argon matrix within the temperature range of 8–28 K. On the other hand, in thin film of pure diketo tautomer, the conversion initiates only when the film is heated at temperatures above 165 K. The observed threshold appears to be associated with excitation of the intermolecular modes, and the IR spectra recorded at high temperatures display narrowing of vibrational bandwidths, which has been associated with reorientations of the molecules in the film. The nonoccurrence of tautomer...