Search results for "Quantum"
showing 10 items of 9714 documents
Casimir-Polder force density between an atom and a conducting wall
2007
In this paper we calculate the Casimir-Polder force density (force per unit area acting on the elements of the surface) on a metallic plate placed in front of a neutral atom. To obtain the force density we use the quantum operator associated to the electromagnetic stress tensor. We explicitly show that the integral of this force density over the plate reproduces the total force acting on the plate. This result shows that, although the force is obtained as a sum of surface element-atom contributions, the stress-tensor method includes also nonadditive components of Casimir-Polder forces in the evaluation of the force acting on a macroscopic object.
Dipole Moment Surface of the van der Waals Complex CH4–N2
2010
The interaction-induced dipole moment surface of the van der Waals CH(4)-N(2) complex has been calculated for a broad range of intermolecular separations R and configurations in the approximation of the rigid interacting molecules at the MP2 and CCSD(T) levels of theory using the correlation-consistent aug-cc-pVTZ basis set with the basis set superposition error correction. The simple model to account for the exchange effects in the range of small overlap of the electron shells of interacting molecules and the induction and dispersion interactions for large R has been suggested. This model allows describing the dipole moment of van der Waals complexes in analytical form both for large R, wh…
Alternative single-reference coupled cluster approaches for multireference problems: the simpler, the better.
2011
We report a general implementation of alternative formulations of single-reference coupled cluster theory (extended, unitary, and variational) with arbitrary-order truncation of the cluster operator. These methods are applied to compute the energy of Ne and the equilibrium properties of HF and C(2). Potential energy curves for the dissociation of HF and the BeH(2) model computed with the extended, variational, and unitary coupled cluster approaches are compared to those obtained from the multireference coupled cluster approach of Mukherjee et al. [J. Chem. Phys. 110, 6171 (1999)] and the internally contracted multireference coupled cluster approach [F. A. Evangelista and J. Gauss, J. Chem. …
An ab initio study of the tautomeric equilibria of the N-oxides of hydroxypyridines in the vapour phase
1993
Abstract An ab initio self-consistent field molecular orbital study of the N-oxides of hydroxypyridines has been carried out. The optimized structures have been obtained at the 6-31G ∗ level, and the energy values have been computed at the 6-31G ∗ and MP2-6-31G ∗ //6-31G ∗ levels. The tautomerization energies for the three couples of systems in the vapour phase have been evaluated.
A theoretical determination of the dissociation energy of the nitric oxide dimer
1994
Multi-reference CI methods have been applied to determine the dissociation energy and structure of thecis-N2O2 molecule. The convergence of the theoretical result has been checked with respect to a systematic expansion of the one-electron basis set and the multi-reference CI wave function. The best calculated value, 13.8 kJ/mol, is in agreement with the experimental value, 12.2 kJ/mol. It has been obtained with an extended ANO-type basis set [6s5p3d2f], including the effect of the basis set superposition error (BSSE) in the geometry optimization, and additional effects, such as the electron correlation of core electrons and relativistic corrections, using the average coupled pair functional…
Precīzie kvantu algoritmi, izmantojot 1-kvantu-vaicājuma izsaukumus
2018
Darbā ir analizēti zināmi unikāli precīzie kvantu algoritmi, kuru īpašības ir atšķirīgas no citiem literatūrā atrodamiem algoritmiem, un uzsākts pētīt iespējas vispārināt šajos algoritmos esošos paņēmienus. Darbā ir noformulēts jauns skaitļošanas modelis, kas ir saistīts ar precīzo kvantu vaicājumu modeli. Veikti skaitliski aprēķini, lai palīdzētu saprast jaunā modeļa iespējas un ierobežojumus. Izteiktas hipotēzes un virzieni, kādos turpināt analīzi un pētījumu.
Many-body Green's function theory of electrons and nuclei beyond the Born-Oppenheimer approximation
2020
The method of many-body Green's functions is developed for arbitrary systems of electrons and nuclei starting from the full (beyond Born-Oppenheimer) Hamiltonian of Coulomb interactions and kinetic energies. The theory presented here resolves the problems arising from the translational and rotational invariance of this Hamiltonian that afflict the existing many-body Green's function theories. We derive a coupled set of exact equations for the electronic and nuclear Green's functions and provide a systematic way to approximately compute the properties of arbitrary many-body systems of electrons and nuclei beyond the Born-Oppenheimer approximation. The case of crystalline solids is discussed …
A Promising Family of Fluorescent Water-Soluble aza-BODIPY Dyes for in Vivo Molecular Imaging.
2019
A new family of water-soluble and bioconjugatable aza-BODIPY fluorophores was designed and synthesized using a boron- functionalization strategy. These dissymmetric bis-ammonium aza-BODIPY dyes present optimal properties for a fluorescent probe; i.e., they are highly water-soluble, very stable in physiological medium; they do not aggregate in PBS, possess high quantum yield; and finally, they can be easily bioconjugated to antibodies. Preliminary in vitro and in vivo studies were performed for one of these fluorophores to image PD-L1 (Programmed Death-Ligand 1), highlighting the high potential of these new probes for future in vivo optical imaging studies.
Development of an Easily Bioconjugatable Water-Soluble Single-Photon Emission-Computed Tomography/Optical Imaging Bimodal Imaging Probe Based on the …
2021
A water-soluble fluorescent aza-BODIPY platform (Wazaby) was prepared and functionalized by a polyazamacrocycle agent and a bioconjugable arm. The resulting fluorescent derivative was characterized and bioconjugated onto a trastuzumab monoclonal antibody as a vector. After bioconjugation, the imaging agent appeared to be stable in serum (>72 h at 37 °C) and specifically labeled HER-2-positive breast tumors slices. The bioconjugate was radiolabeled with [111In] indium and studied in vivo. The developed monomolecular multimodal imaging probe (MOMIP) is water-soluble and chemically and photochemically stable, emits in the near infrared (NIR) region (734 nm in aqueous media), and displays a goo…
Driven Bose-Hubbard Model with a Parametrically Modulated Harmonic Trap
2016
We investigate a one-dimensional Bose–Hubbard model in a parametrically driven global harmonic trap. The delicate interplay of both the local interaction of the atoms in the lattice and the driving of the global trap allows us to control the dynamical stability of the trapped quantum many-body state. The impact of the atomic interaction on the dynamical stability of the driven quantum many-body state is revealed in the regime of weak interaction by analyzing a discretized Gross–Pitaevskii equation within a Gaussian variational ansatz, yielding a Mathieu equation for the condensate width. The parametric resonance condition is shown to be modified by the atom interaction strength. In particul…