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1.
《International journal of quantum chemistry》2018,118(16)
Algorithms to build the basis and matrix representation to obtain the Kramers configuration space functions (KCSFs) via diagonalization will be formally generalized to an arbitrary number of unpaired (open shell) fermions. Effective build up of the matrix representation will be outlined (including threading and graphical processing unit parallelism) to subsequently obtain the KCSFs via calling external/numerical library routines for diagonalization. The effective build up of the matrix representation relays on a binary tree search algorithm to allow evaluation the action on a given basis vector. The binary tree search avoids the treatment of zero matrix elements which leads to an exponential acceleration. The implementation ( basis creation, matrix representation, and matrix diagonalization) will be done in an all in core and all at once manner, hence the available core memory sets the physical limits in practical applications. Memory limitations, sparsity of the matrix, general case of n fermions in m spinors, and the application of KCSFs will be put into further perspective. 相似文献
2.
《International journal of quantum chemistry》2018,118(13)
The electronic structure of several many‐electron atoms, confined within a penetrable spherical box, was studied using the Hartree–Fock (HF) method, coupling the Roothaan's approach with a new basis set to solve the corresponding one‐electron equations. The resulting HF wave‐function was employed to evaluate the Shannon entropy, , in configuration space. Confinements imposed by impenetrable walls induce decrements on when the confinement radius, Rc, is reduced and the electron‐density is localized. For confinements commanded by penetrable walls, exhibits an entirely different behavior, because when an atom starts to be confined, delivers values less than those observed for the free system, in the same way that the results presented by impenetrable walls. However, from a confinement radius, shows increments, and precisely in these regions, the spatial restrictions spread to the electron density. Thus, from results presented in this work, the Shannon entropy can be used as a tool to measure the electron density delocalization for many‐electron atoms, as the hydrogen atom confined in similar conditions. 相似文献
3.
《International journal of quantum chemistry》2018,118(14)
Comprehensive investigations on the structural modifications of negative hydrogen ion within an impenetrable spherical domain has been performed in the framework of Ritz variational method. Electron correlation plays a major role in the formation of H– ion. The Hylleraas‐type basis set expansion of wave function considered here incorporates the effect of electron correlation in an explicit manner. Energy values of and 1sn states of H– ion within confined domain have been calculated. Although the singly excited states do not exist for a “free” H– ion, well converged energy values of such states have been found within a wide range of confinement radius. The thermodynamic pressure felt by the ion inside the sphere is also estimated. The general trend shows successive destabilization of the excited energy levels with increase of pressure. The contribution of angular correlation in the energy values have been estimated. Evolution of and energy levels of H– ion as quasi‐bound states are being reported. 相似文献
4.
Full–dimensional quantum molecular dynamics calculations of the rovibrationally mediated X
→ 2
transition of nitrous oxide
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Mohammad Noh Daud 《International journal of quantum chemistry》2016,116(6):452-468
A full dimensional time‐dependent quantum wavepacket approach is used to study the photodissociation dynamics of nitrous oxide for the X → 2 bound–bound transition based on new highly accurate potential energy and transition dipole moment surfaces. The computed 2 absorption spectra at room temperature are characterized by sharp vibrational structures that contribute slightly to the diffuse vibrational structures around the maximum peak at 180 nm of the first ultraviolet absorption band (from the contribution of 2 , 1 , and 2 states) of N2O. Transitions from different initial rovibrational states reveal that the sharp structures arise mainly from N2? O bending vibrations, whereas, at higher temperatures, the N2? O and N? NO stretching vibrations are responsible for enhancing the intensity of the structures. At absorption wavelengths 166 nm and 179 nm, vibrational quantum state distributions of N2 product fragments decrease monotonically with increasing vibrational quantum number v = 0, 1, 2. At 166 nm, rotational quantum state distributions of N2 at fixed v = 0 and v = 1 display multimodal profiles with maximum peaks at j = 77 and j = 75, respectively, whereas, the distributions at the 179 nm absorption wavelength display bimodal profiles with maximum peaks at j = 73 and j = 71, respectively. Accordingly, the presence of rotationally hot N2 from previous experimental and theoretical works in the first band strongly implies a significant influence of the 2 state in determining the final dissociation pathway of N2 + O. © 2016 Wiley Periodicals, Inc. 相似文献
5.
《International journal of quantum chemistry》2018,118(16)
The bonding problem in borazine (B3N3H6), boroxine (B3O3H3), and carborazine (B2N2C2H6) is successfully addressed through the consideration of the excited states of the constituent fragments, namely BH( ), NH( ), and CH( ). We propose the participation of resonant structures for all three species that help to explain the experimental findings. A discussion on the chemical pattern of the parental molecule benzene (C6H6) helps to make coherent the whole bonding analysis on the titled species. 相似文献
6.
Geometric and electronic structures of silicon fluorides
(N = 4 – 6) and potential energy surfaces for dissociation reactions
→ SiF4 + F– and
→
+ F–
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Vitaliy V. Koval Ruslan M. Minyaev Vladimir I. Minkin 《International journal of quantum chemistry》2016,116(18):1358-1361
The geometric and electronic structures of a series of silicon fluorides (n = 4 ? 6) were computationally studied with the aid of density functional theory (DFT) method with B3LYP and M06‐2X functionals and coupled cluster (CCSD and CCSD(T)) methods with 6‐311++G(d,p) basis set. The nature of the Si‐F bonds in these compounds was analyzed in the framework of the natural bond orbital theory and natural resonance theory. Energy characteristics (heats of reactions and energy barriers) of the dissociation reactions → SiF4 + F– and → + F– were calculated using the DFT and CCSD methods. The potential energy surface of elimination of a fluoride anion from has a specific topology with valley‐ridge inflection points corresponding to bifurcations of the minimal energy reaction path. © 2016 Wiley Periodicals, Inc. 相似文献
7.
Theoretical prediction of the optical rotation of chiral molecules in ordered media: A computational study of (Ra)‐1,3‐dimethylallene, (2R)‐2‐methyloxirane,and (2R)‐N‐methyloxaziridine
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Maria C. Caputo Stefano Pelloni Paolo Lazzeretti 《International journal of quantum chemistry》2015,115(14):900-906
A theoretical procedure has been developed and implemented to calculate the optical rotation of chiral molecules in ordered phase via origin‐independent diagonal components , of the optical activity tensor and origin‐independent components , for , of the mixed electric dipole‐electric quadrupole polarizability. Origin independence was achieved by referring these tensors to the principal axis system of the electric dipole dynamic polarizability at the same laser frequency ω. The approach has been applied, allowing for alternative quantum mechanical methods based on different gauges, to estimate near Hartree–Fock values for three chiral molecules, (2R)‐N‐methyloxaziridine C2NOH5, (2R)‐2‐methyloxirane (also referred to as propylene oxide) C3OH6, and ( )‐1,3‐dimethylallene C5H8, at two frequencies. The theoretical predictions can be useful for an attempt at measuring correspondent experimental values in crystal phase. © 2015 Wiley Periodicals, Inc. 相似文献
8.
《International journal of quantum chemistry》2018,118(10)
A new series of divalent boron‐rare gas cations (Rg = He ∼ Rn, n = 1–4) have been predicted theoretically at the B3LYP, MP2, and CCSD(T) levels to present the structures, stability, charge distributions, bond natures, and aromaticity. The Rg B bond energies are quite large for heavy rare gases and increase with the size of the Rg atom. Because of steric hindrance new Rg atoms introduced to the B4 ring will weaken the Rg B bond. Thus in the Rg B bond has the largest binding energy 90–100 kcal/mol. p‐ has a slightly shorter Rg B bond length and a larger bond energy than o‐ . NBO and AIM analyses indicate that for the heavy Rg atoms Ar ∼ Rn the B Rg bonds have character of typical covalent bonds. The energy decomposition analysis shows that the σ‐donation from rare gases to the boron ring is the major contribution to the Rg B bonding. Adaptive natural density partitioning and nuclear‐independent chemical shift analyses suggest that both and have obvious aromaticity. 相似文献
9.
The Franck-Condon factors and r centroids for the first negative and the second negative band systems of the molecule, based on the Rydberg-Klein-Rees potential energy curves, have been computed. The variation of the electronic transition moment with the internuclear separation has been studied for the first negative bands and the Einstein A coefficients, the oscillator strengths, and the absolute band strengths for this system have been calculated by adopting the recent experimental data on the lifetimes of the various levels of the excited B state. On a calculé pour la molécule les facteurs de Franck-Condon et les r centroïds pour les deux premiers systèmes de bandes négatives avec des courbes de potential de Rydberg-Klein-Rees. On a étudié la variation du moment de transition éléctronique avec la séparation internucléaire pour les premières bandes négatives. Les constantes A d'Einstein, les forces d'oscillateur et les intensités absolues des bandes ont été calculé des données expérimentales récentes sur les durées de vie des niveaux différents de l'état excité B . Die Franck-Condon-Faktoren und die r-Zentroide der zwei ersten negativen Banden-systeme des -Moleküls, wurden mit den Rydberg-Klein-kees Potentialkurven berechnet. Die Variation des elektronischen Übergangsmoment mit dem Kernabstand würde für die ersten negativen Bänder studiert. Die Einsteinschen A-Koeffizienten, die Oszillatorstärken and die absoluten Bandenstärken wurden mit die neuen experimentellen Tatsachen über die Lebensdauern der verschiedenen Niveaus des angeregten B Zustands berechnet. 相似文献
10.
《International journal of quantum chemistry》2018,118(14)
Energy eigenvalues of nonautoionizing doubly excited states originating from 2pnf ( ) configuration of two‐electron atoms have been calculated by expanding the basis set in explicitly correlated Hylleraas coordinates under the framework of Ritz variational method. A detailed discussion on the evaluation of correlated basis integrals is given. The energy eigenvalues of a number of these doubly excited states are being reported for the first time especially for the high lying states. The effective quantum numbers ( ) for the states mentioned above have been calculated by using the theory of quantum defect. 相似文献
11.
A theoretical study on the stability difference of the borane
and carborane C2Bn−2Hn (5 ≤ n ≤ 7) clusters
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In order to study the electronic structure and structural stability of borane and carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters, especially the stability difference between the borane and carborane C2B3H5. The frontier orbital energy levels of the borane and carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters are calculated at CCSD(T)/aug‐cc‐pVXZ//B3LYP/def2‐TZVPP level. The results are further analyzed by qualitative frontier orbital method based on the cap–ring interaction. The results reveal that: (1) the larger Egap(HOMO‐LUMO energy gap) of carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters than borane (5 ≤ n ≤ 7) clusters originates from the more effective cap–ring orbital overlap of carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters than that of borane (5 ≤ n ≤ 7) clusters; (2) the smallest Egap of the borane results from the highest energy level of the ring symmetry‐adapted linear combination orbital of cluster; and (3) the largest Egap of the carborane C2B3H5 is induced by the most effective cap–ring orbital interaction of C2B3H5 cluster. © 2014 Wiley Periodicals, Inc. 相似文献
12.
Theoretical investigation of the weak interactions of rare gas atoms with silver clusters by resonance Raman spectroscopy modeling
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The interactions of rare gas atoms (Rg = Ar, Kr, and Xe) with small neutral and cationic silver clusters have been investigated by density functional methods and the effect of these weak interactions on the resonance Raman spectra of the complexes has been evaluated. The resonance Raman technique that depends on the properties of ground and excited state, seems deeply sensitive to the weak rare gas–metal cluster interactions, and the use of inert gases has been proven to be an excellent approach to recognize the ability of this technique to detect extremely weak interactions. In this work, for , and complexes the IR, normal and resonance Raman spectra have been calculated and the effect of rare gas–cluster stretching vibration ( ) on the pattern and the relative intensities of different spectra have been investigated. The resonance Raman spectra for the weakly interacted complexes (with the interaction energies less than ?2.0 kcal/mol) exhibit the vibration with the detectable intensity that its intensity increases by going from Ag6–Ar to Ag6–Xe complex. Moreover, the resonance Raman spectra (based on the excited state gradient approximation) for high intensity nearly degenerate excited states, proved the effect of accumulation of the excited state charge density on the relative intensity of vibration. 相似文献
13.
《International journal of quantum chemistry》2018,118(17)
Stochastic fluctuation of barrier height and width of a symmetric double well plays a very significant role in the corresponding dynamics by increasing the semiclassical transmission probability and Shannon entropy of the system. The population of the system has been observed to be spread into several under barrier states starting from the or [, where and are the wave functions describing the two lowest degenerate states] in presence of the stochastic fluctuation. This distribution over several states is manifested by steady increase in Shannon entropy. However, any arbitrary value of the stochastic fluctuation cannot increase the populations of the upper energy states and consequently no gain in the net value of Shannon entropy results. There is an optimum frequency for which the Shannon entropy passes through a maximum, which is also found out in this work. We have also calculated the semiclassical WKB like transmission probability as a function of time and it is clear that the random fluctuation of barrier causes the transmission probability to increase to a significant amount. As the total energy of the system remains below the potential barrier, this transmission probability is equivalent to tunneling probability. It has been clearly shown that if the fluctuation is made to be periodic (without changing the frequency and magnitude of the fluctuation) it cannot effect any significant change in the overall dynamics. 相似文献
14.
Energies for cyclic and acyclic aggregations of adamantane and diamantane units sharing vertices,edges, or six‐membered rings
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Alexandru T. Balaban Debojit Bhattacharya Douglas J. Klein Yenni P. Ortiz 《International journal of quantum chemistry》2016,116(2):113-122
Diamondoids are hydrocarbons having a carbon scaffold comprised from polymer‐like composites of adamantane cages. This article describes computed total energies and “SWB‐tension” energies (often referred to as “strain” energies) for species having n adamantane or diamantane units sharing pairwise: one carbon atom (spiro‐[n]adamantane or spiro‐[n]diamantane); one C? C bond (one‐bond‐sharing‐[n]adamantane or one‐bond‐sharing‐[n]diamantane); or one chair‐shaped hexagon of carbon atoms (1234‐helical‐cata‐[n]diamantanes). Each of the five investigated polymer‐like types is considered either as an acyclic or a cyclic chain of adamantane‐ or diamantane‐unit cages. With increasing n values, SWB‐tension energies for acyclic aggregates are found to increase linearly, while the net SWB‐tension energies of cyclic aggregates often go thru a minimum at a suitable value of . In all five cases, a limiting common energy per unit ( ) is found to be approached by both cyclic and acyclic chains as , as revealed from plots of versus 1/n for acyclic chains and of versus 1/n2 for cyclic chains. © 2015 Wiley Periodicals, Inc. 相似文献
15.
Dealing with the shifted and inverted Tietz–Hua oscillator potential using the J‐matrix method
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Mohamed S. Abdelmonem Afaf Abdel‐Hady Ibraheem Nasser 《International journal of quantum chemistry》2016,116(12):897-907
The tridiagonal J‐matrix approach has been used to calculate the low and moderately high‐lying eigenvalues of the rotating shifted Tietz–Hua (RSTH) oscillator potential. The radial Schrödinger equation is solved efficiently by means of the diagonalization of the full Hamiltonian matrix, with the Laguerre or oscillator basis. Ro–vibrational bound state energies for 11 diatomic systems, namely , , , NO, CO, , , , , , and NO+, are calculated with high accuracy. Some of the energy states for molecules are reported here for the first time. The results of the last four molecules have been introduced for the first time using the oscillator basis. Higher accuracy is achieved by calculating the energy corresponding to the poles of the S‐matrix in the complex energy plane using the J‐matrix method. Furthermore, the bound states and the resonance energies for the newly proposed inverted Tietz–Hua IRSTH‐potential are calculated for the H2‐molecule with scaled depth. A detailed analysis of variation of eigenvalues with n, quantum numbers is made. Results are compared with literature data, wherever possible. © 2015 Wiley Periodicals, Inc. 相似文献
16.
Lukáš Bučinský Michal Malček Stanislav Biskupič 《International journal of quantum chemistry》2016,116(13):1040-1048
Many fermions Kramers pairs formalism is considered from the prospective of the sum of individual single fermion time‐reversal operators. The obtained many fermions “pseudo Kramers pairs operator” ( ), as well as its square ( ), have formally the same structure as the many fermion spin operators and . Nevertheless, the shape of eigenfunctions with respect to and is different. Herein all Kramers adapted eigenfunctions of for cases of up to four unpaired fermions are compiled, and their properties with respect to further advocated. It will be shown that degeneracy of the multiplets recovers the proper behavior with respect to Pascal's triangle. A projection operator for obtaining the “high spin” Kramers adapted eigenfunctions is suggested. Noncommutation of with spin and angular momentum operators and degeneracy is discussed at last. © 2016 Wiley Periodicals, Inc. 相似文献
17.
Carbon–sulfur chains: A high‐resolution infrared and quantum‐chemical study of C3S and SC7S
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John B. Dudek Thomas Salomon Sven Fanghänel Sven Thorwirth 《International journal of quantum chemistry》2017,117(18)
In the course of a 5 μm high‐resolution infrared study of laser ablation products from carbon–sulfur targets, the ν1 vibrational mode region of linear C3S has been studied continuously from 2046 to 2065 cm?1. Besides the prominent vibrational fundamental, the region was found to feature the , and even hot bands, the latter two of which were observed for the first time. Owing to the high signal‐to‐noise ratio obtained, the ν1 mode of S could also be observed in natural abundance for the first time at high spectral resolution in the infrared. At 2061 cm?1, hidden inside the branch of the C3S ν1 fundamental mode, a weak new band is observed which exhibits very tight line spacing and stems from a heavy both carbon and sulfur containing carrier. On the basis of high‐level quantum‐chemical calculations of selected carbon–sulfur chains and other carbon‐rich cumulenes, this feature is attributed to the ν5 vibrational fundamental of linear SC7S, which stands for the first gas‐phase spectroscopic detection of this long cumulenic chain. 相似文献
18.
Simulated annealing‐based optimal control over tunneling process through SDWP and Eckart barrier: A momentum basis representation
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Srijeeta Talukder Pinaki Chaudhury Subhasree Ghosh 《International journal of quantum chemistry》2017,117(15)
For a reaction to proceed via tunneling mechanism, it is essential that the reactants will cross the potential barrier (EP), where its initial energy (E0) is below the potential barrier EP. Tunneling probability τ is defined as the probability of having momentum higher than km, where . In the momentum basis representation, τ can be directly calculated by integrating from the limit km to infinity, where is the wave function in the momentum space. Instead of the continuous basis, if we chose momentum grid space, τ can be expressed as . Our target here is to increase this τ by applying a polychromatic field, so that the reaction rate can be enhanced. By applying Simulated Annealing technique we have designed some polychromatic electric fields, spatially symmetric and asymmetric type, which enhances the tunneling rate in symmetric double well system and Eckart barrier confined in an infinite well. 相似文献
19.
The H,H2+, and HeH2+ systems confined by an impenetrable spheroidal cavity: Revisited study via the Lagrange‐mesh approach
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The one electron systems H, H , and HeH confined by an impenetrable spheroidal cavity are revisited in the frame of the Lagrange‐mesh method. The Born–Oppenheimer approximation where the nuclei are clamped at the foci is considered. Benchmark results of the total energy are obtained as a function of the interfocal distance R and the eccentricity of the cavity . Dipole oscillator strengths are calculated for the molecular ions H and HeH . 相似文献
20.
Quantum control of electron‐proton symmetry breaking in dissociative ionization of H2 by intense laser pulses
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Mohammad Noh Daud Huizhong Lu Szczepan Chelkowski Andre D. Bandrauk 《International journal of quantum chemistry》2015,115(6):369-380
Forward and backward electron/proton ionization/dissociation spectra from one‐dimensional non‐Born‐Oppenheimer H2 molecule exposed to ultrashort intense laser pulses ( W/cm2, λ = 800 nm) have been computed by numerically solving the time‐dependent Schrödinger equation. The resulting above‐threshold ionization and above‐threshold dissociation spectra exhibit the characteristic forward‐backward asymmetry and sensitivity to the carrier‐envelope phase (CEP), particularly for high energies. A general framework for understanding CEP effects in the asymmetry of dissociative ionization of H2 has been established. It is found that the symmetry breaking of electron‐proton distribution with π periodic modulation occurs for all CEPs except for ( integer) and the largest asymmetry coming from the CEP of . At least one of the electron and proton distributions is asymmetric when measured simultaneously. Inspection of the nuclear and electron wave packet dynamics provides further information about the relative contribution of the gerade and ungerade states of to the dissociation channel and the time delay of electrons in asymmetric ionization. © 2014 Wiley Periodicals, Inc. 相似文献