نتایج جستجو برای: cluster expansion
تعداد نتایج: 339939 فیلتر نتایج به سال:
Small weakly bound boson-fermion 4He(m) 3He(n) clusters formed in a free jet expansion are identified using nondestructive transmission grating diffraction. The observations confirm the existence of more than 11 very tenuous complexes including the three-body halo molecule 4He2 3He and the pseudo-Borromean complex 4He2 3He2. Effective cluster formation temperatures, extracted from a sudden free...
A generalisation of the pure site and pure bond percolation problems is studied, in which both the sites and bonds are independently occupied at random. This generalisa-tion-the site-bond problem-is of current interest because of its application to the phenomenon of polymer gelation. Motivated by considerations of cluster connectivity, we have defined two distinct models for site-bond percolati...
In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z = 0.54 elliptical galaxy in the MACS J...
Four Hubble diagrams are combined to test for the linearity of the cosmic expansion field. The expansion rate, H0, is found to decrease by ∼ 5% out to 18 000 km s. Beyond this distance the mean value of H0 is close to the value at 10 000 km s. The absolute value of H0 is derived in two different ways. The one leads through Cepheids from HST and blue SNe Ia to H0 = 57± 7 (external error) at 30 0...
We study the thermodynamics of cubic Ti 1−x Al x N using a unified cluster expansion approach for the alloy problem. The purely configurational part of the alloy Hamiltonian is expanded in terms of concentration-and volume-dependent effective cluster interactions. By separate expansions of the chemical fixed lattice, and local lattice relaxation terms of the ordering energies, we demonstrate ho...
Despite their geometric simplicity, the crystal structures L11 (CuPt) and L13 (CdPt3) do not appear as ground states experimentally, except in Cu-Pt. We investigate the possibility that these phases are ground states in other binary intermetallic systems, but overlooked experimentally. Via the synergy between high-throughput and cluster-expansion computational methods, we conduct a thorough sea...
Let z be a real quadratic irrational. We compare the asymptotic behavior of Dedekind sums S(pk, qk) belonging to convergents pk/qk of the regular continued fraction expansion of z with that of Dedekind sums S(sj/tj) belonging to convergents sj/tj of the negative regular continued fraction expansion of z. Whereas the three main cases of this behavior are closely related, a more detailed study of...
We report coefficients of the h-bond expansion of the bridge function of the hard-sphere system up to order rho(4) (where rho is the density in units of the hard-sphere diameter), which in the highest-order term includes 88 cluster diagrams with bonds representing the total correlation function h(r). Calculations are performed using the recently introduced Mayer-sampling method for evaluation o...
Benjamini, Lyons and Schramm (1999) considered properties of an infinite graph G, and the simple random walk on it, that are preserved by random perturbations. To address problems raised by those authors, we study simple random walk on the infinite percolation cluster in Cayley graphs of certain amenable groups known as “lamplighter groups”. We prove that zero speed for random walk on a lamplig...
The effect of structural relaxations in alloys is described using a multibody energy expansion formalism. N-body potentials in the multibody expansion are computed from energies of isolated clusters, which, in turn, are calculated from empirical potentials or self-consistent quantum mechanical calculations. Convergence characteristics of multibody expansions MBEs are improved by weighting energ...
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