Search results for "INTERACTION"
showing 10 items of 5710 documents
Analytic second derivatives for general coupled-cluster and configuration-interaction models.
2004
Analytic second derivatives of energy for general coupled-cluster (CC) and configuration-interaction (CI) methods have been implemented using string-based many-body algorithms. Wave functions truncated at an arbitrary excitation level are considered. The presented method is applied to the calculation of CC and CI harmonic frequencies and nuclear magnetic resonance chemical shifts up to the full CI level for some selected systems. The present benchmarks underline the importance of higher excitations in high-accuracy calculations.
The effect of triple excitations in coupled cluster calculations of frequency-dependent polarizabilities
1998
Abstract Frequency-dependent polarizabilities have been implemented within the CC3 model. Comparison with full configuration interaction results shows that the triple excitation effects included in CC3 lead to a significantly improved treatment for the dispersion of the polarizability of CH+. For the refractivity and polarizability anisotropy of N2, better agreement with experiment is found for the CC3 results than for those obtained with the coupled cluster singles and doubles model.
Full configuration-interaction and coupled-cluster calculations of the indirect spin–spin coupling constant of BH
2003
Abstract Full configuration-interaction calculations of the indirect spin–spin coupling constant of the BH molecule have been carried out in order to investigate the performance of various coupled-cluster (CC) methods in the treatment of electron-correlation effects, while the corresponding basis set convergence is analyzed in CC singles and doubles calculations. Assuming additivity of correlation and basis set effects, a theoretical estimate of 50.67 Hz is obtained for the 11 B 1 H spin–spin coupling constant.
Spin-orbit coupling constants from coupled-cluster response theory
2000
A scheme for the calculation of spin-orbit coupling constants using coupled-cluster (CC) electronic structure methods is described based on response-theory expressions for transition properties. An implementation is reported for singlet–triplet transitions within the coupled-cluster singles and doubles (CCSD) approximation. An atomic mean-field representation of the spin-orbit interaction is used to simplify the calculation of spin-orbit coupling constants. Sample calculations are presented for spin-orbit couplings for the 11Σ+→13Π transitions for BH and AlH and for the 11A′→13A″ and the 13A″→11A″ transitions for the silylenes HSiX, X=F, Cl, Br, and are compared to results obtained from ful…
Exchange Coupling in Cyano-Bridged Homodinuclear Cu(II) and Ni(II) Complexes: Synthesis, Structure, Magnetism, and Density Functional Theoretical St…
2001
The synthesis and structural characterization of several new cyano-bridged copper(II) and nickel(II) homodinuclear complexes is presented. The measure of magnetic properties for these complexes is complemented with a computational study of the exchange coupling for several model structures representing this family of compounds. The influence of several factors on the coupling constant has been examined, coordination position occupied by the bridging ligand, distortions of the coordination environment, and relative disposition of the cyanide ion with respect to the M-M vector. Comparison of experimental and calculated coupling constants allows for the rationalization of the most relevant fea…
Mesonic enhancement of the weak axial charge and its effect on the half-lives and spectral shapes of first-forbidden J+↔J− decays
2018
The effects of the enhancement of the axial-charge matrix element γ5 were studied in medium heavy and heavy nuclei for first-forbidden J+↔J− decay transitions using the nuclear shell model. Noticeable dependence on the enhancement ϵMEC of the axial-charge matrix element, as well as on the value of the axial-vector coupling constant gA was found in the spectral shapes of $^{93}$Y, $^{95}$Sr, and $^{97}$Y. The importance of the spectrum of $^{138}$Cs in the determination of gA is discussed. Half-life analyses in the A≈95 and A≈135 regions were done, and consistent results gA≈0.90, 0.75, and 0.65, corresponding to the three enhancement scenarios ϵMEC=1.4, 1.7, and 2.0, were obtained. Connectio…
Dark matter from unification
2013
We consider a minimal extension of the Standard Model (SM), which leads to unification of the SM coupling constants, breaks electroweak symmetry dynamically by a new strongly coupled sector and leads to novel dark matter candidates. In this model, the coupling constant unification requires the existence of electroweak triplet and doublet fermions singlet under QCD and new strong dynamics underlying the Higgs sector. Among these new matter fields and a new right handed neutrino, we consider the mass and mixing patterns of the neutral states. We argue for a symmetry stabilizing the lightest mass eigenstates of this sector and determine the resulting relic density. The results are constrained …
Lateral indirect exchange coupling in a two-dimensional nanostripe array
2002
We observe a lateral indirect exchange coupling in a multistripe system of parallel Fe nanostripes grown by self-organized growth on a vicinal single-crystal W(110) surface. The width and the distance between the stripes of monolayer height were modified via the total amount of deposited Fe. The easy axis of the magnetization lies perpendicular to the stripe edges and in the surface plane, thus resulting in a ferromagnetic dipolar coupling. In addition to the dipolar coupling we observe an antiferromagnetic indirect exchange coupling for the nanostripe system covered by Au. The coupling causes a superferromagnetic phase transition in the nanostripe array.
Spin-orbit-torque-induced skyrmion dynamics for different types of spin-orbit coupling
2018
Abstract We investigate current-induced skyrmion dynamics in the presence of Dzyaloshinskii-Moriya interaction and spin-orbit spin-transfer torque corresponding to various types of spin-orbit coupling. We determine the symmetries of Dzyaloshinskii-Moriya interaction and spin-orbit spin-transfer torque based on linear spin-orbit coupling model. We find that like interfacial Dzyaloshinskii-Moriya interaction (Rashba spin-orbit coupling) and bulk Dzyaloshinskii-Moriya interaction (Weyl spin-orbit coupling), Dresselhaus spin-orbit coupling also has a possibility for stabilizing skyrmion and current-induced skyrmion dynamics.
Radiatively Induced Neutrino Masses and Large Higgs-Neutrino Couplings in the Standard Model with Majorana Fields
1999
The Higgs sector of the Standard Model with one right-handed neutrino per family is systematically analyzed. In a model with intergenerational independent mixings between families, we can account for very light neutrinos acquiring Majorana masses radiatively at the first electroweak loop level. We also find that in such a scenario the Higgs coupling to the light-heavy neutrinos and to the heavy-heavy ones may be remarkably enhanced with significant implications for the production of these heavy neutrinos at high energy colliders.