Analysis of structures and melting properties of the 19-atom Ni–Co clusters

In this paper, by using the classical molecular dynamics method and the GEAM potential, the geometric structure and the melting properties of the 19-atom Ni – Co clusters with different compositions are studied. It is found that all the clusters have the double icosahedron structures although some of the structures are slightly deformed. With the increase of the temperature, a pre-melting phenomenon is observed. The pre-melting temperatures of the pure cobalt and nickel clusters are very close. But on the whole, the pre-melting temperature decreases with the increase of the number of the nickel atom for the mixed clusters. The effects of the substitution atoms on the melting temperature of the clusters are similar to that on the pre-melting temperature although there are some oscillations in the decrease process. The mechanism of these findings are also investigated and analyzed.

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Structural and dynamical properties of 13-atom Cu–Co mixed clusters

International Journal of Modern Physics C ◽

10.1142/s0129183122500723 ◽

2021 ◽

Author(s):

Shi-Wei Ren

Keyword(s):

Molecular Dynamics ◽

Pure Copper ◽

Similarity Function ◽

Step Process ◽

Pure Cobalt ◽

Pair Separation ◽

Dynamical Properties ◽

Mixed Clusters ◽

Dynamics Method ◽

Relative Root

In this paper, the geometric structures and the melting-like processes of the 13-atom pure copper, pure cobalt cluster and their 13-atom mixed clusters are investigated and compared by the molecular dynamics method. The calculation shows that the pure copper and cobalt clusters have the standard icosahedral structures and the mixed clusters take on the deformed icosahedral structures. The quantitative analysis shows that the deformations are slight. Moreover, an element similarity function is introduced by which the contribution of the compositions of the clusters to the deformation of the mixed clusters is analyzed and discussed. With the increase of the temperature, the migrating and recombination of the atoms on the surface of the clusters are observed, indicating the starting of the transition from solid-like to liquid-like state for the clusters. Through the calculating of the relative root-mean-squared pair separation fluctuation and monitoring the dynamical structures of the clusters, it is found that the mixed clusters experience a multi-step process in the transition.

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Effects of B2O3 and CaF2 on Melting Properties of CaO-Based Slags

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.217-219.511 ◽

2012 ◽

Vol 217-219 ◽

pp. 511-514

Author(s):

Hong Ming Wang ◽

De Fu ◽

Gui Rong Li ◽

Xiang Zhu ◽

Zhao Zhao ◽

...

Keyword(s):

Melting Temperature ◽

Steelmaking Process ◽

Melting Temperatures ◽

Steelmaking Slags ◽

Melting Properties ◽

Fluxing Agent

B2O3 is employed as fluxing agent of CaO-SiO2-Fe2O3 steelmaking slags to substitute for CaF2. The influences of B2O3 and CaF2 on the melting properties of this system slags were investigated and compared. The results indicate that the fluxing effect of B2O3 is more remarkable than that of CaF2. Therefore, B2O3 promotes the dissolution of CaO, SiO2 and 2CaO•SiO2, etc, then the slagging speed can be improved greatly. The melting temperatures of slags increase with the increasing of basicity, especially, when CaF2 is used as fluxing agent as well as the basicity is up to 5.0, the melting temperature is increased higher than 1420°C. These characteristics of boron-containing slgas are more suitable for steelmaking process than those of fluoride-containing slags.

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Icosahedral structure in hydrogenated cobalt and nickel clusters

The Journal of Chemical Physics ◽

10.1063/1.461224 ◽

1991 ◽

Vol 95 (12) ◽

pp. 8919-8930 ◽

Cited By ~ 56

Author(s):

T. D. Klots ◽

B. J. Winter ◽

E. K. Parks ◽

S. J. Riley

Keyword(s):

Icosahedral Structure ◽

Nickel Clusters ◽

Cobalt And Nickel

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Studies on the Melting of DNA

Zeitschrift für Naturforschung C ◽

10.1515/znc-1974-3-405 ◽

1974 ◽

Vol 29 (3-4) ◽

pp. 130-132

Author(s):

Gokul Chandra Das

Keyword(s):

Ionic Strength ◽

Melting Temperature ◽

Thermal Denaturation ◽

Spectrophotometric Methods ◽

Melting Temperatures

Abstract The thermal denaturation of the native DNA in solvents of varying salt concentrations was studied by viscometric and spectrophotometric methods. It was observed that within the molarity range of 0.02 ᴍ to 0.3 ᴍ, the melting temperatures obtained by the two independent methods agreed well, but that at lower ionic strength the agreement was not satisfactory. Both the viscometric and the spectrophotometric measurements showed an increase of the melting temperature with increasing counterion concentration and a levelling off effect in the neighbourhood of 0.3 ᴍ.

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Electronic structures of tetrahedral iron, cobalt, and nickel clusters. Partial quenching of magnetism in partially carbonylated derivatives

The Journal of Chemical Physics ◽

10.1063/1.449155 ◽

1985 ◽

Vol 83 (7) ◽

pp. 3507-3513 ◽

Cited By ~ 45

Author(s):

Gary F. Holland ◽

Donald E. Ellis ◽

William C. Trogler

Keyword(s):

Electronic Structures ◽

Iron Cobalt ◽

Nickel Clusters ◽

Tetrahedral Iron ◽

Cobalt And Nickel

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Crystallization in Stretched Polymer Networks. I. trans-Polychloroprene

Rubber Chemistry and Technology ◽

10.5254/1.3539117 ◽

1967 ◽

Vol 40 (4) ◽

pp. 1071-1083 ◽

Cited By ~ 3

Author(s):

A. N. Gent

Keyword(s):

Melting Temperature ◽

Polymer Networks ◽

Crystal Form ◽

Simple Extension ◽

Theoretical Treatment ◽

Nucleation Kinetics ◽

Segmental Mobility ◽

Melting Temperatures ◽

Direct Measurements ◽

Stress Changes

Abstract Changes in tensile stress afford a simple means of studying the rates of crystallization and the melting temperatures in crosslinked polymers subjected to simple extension. The form and magnitude of the stress changes in networks of trans-polychloroprene are closely similar to those observed for cis-1:4-polyisoprene and cis-l:4-polybutadiene networks. They are in accord with the formation of oriented crystallites and incompatible with folded chain crystallization at extensions as low as 15 per cent. It seems likely that the present networks do not crystallize by chain folding even in the unstretched state. The large increases in rate of crystallization with extension are approximately accounted for by corresponding increases in the equilibrium melting temperature. Direct measurements of the melting temperature show similar rises with extension. The rise in melting temperature is in good agreement with Flory's theoretical treatment of oriented crystallization at extension ratios of three and higher (when the crystallite orientation is complete) for three networks having different degrees of crosslinking. When referred to a constant segmental mobility, namely, that obtaining at Tg+50° C, the rates of crystallization at various extensions obey a common dependence upon the degree of supercooling. This relation is in fair accord with theories of nucleation kinetics, except at the lowest temperatures where there is some indication of the appearance of a new crystal form.

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MAGNETISM IN TRANSITION-METAL CLUSTERS FROM THE ATOM TO THE BULK

Surface Review and Letters ◽

10.1142/s0218625x96000772 ◽

1996 ◽

Vol 03 (01) ◽

pp. 429-434 ◽

Cited By ~ 20

Author(s):

I.M.L. BILLAS ◽

A. CHÂTELAIN ◽

W.A. de HEER

Keyword(s):

Molecular Beam ◽

Magnetic Moments ◽

Beam Deflection ◽

Transition Metal Clusters ◽

Iron Cluster ◽

Iron Cobalt ◽

Nickel Clusters ◽

Magnetic Shell ◽

Superparamagnetic Clusters ◽

Cobalt And Nickel

Molecular beam deflection measurements of small iron, cobalt, and nickel clusters show how magnetism develops as the cluster size is increased from several tens to several hundreds of atoms for temperatures from 80 and 1000 K. Cluster magnetization is found to be superparamagnetic for rotationally warm clusters, where it follows the Langevin function. The magnetization of rotationally cold clusters is anomalous: it is strongly reduced and nonlinear with the applied field. For superparamagnetic clusters, the magnetic moments can be determined from the magnetization. We find that ferromagnetism occurs even for the smallest sizes: for clusters with less than about 30 atoms the magnetic moments are atom-like and as the size is increased up to 700 atoms they approach the bulk limit, with oscillations probably caused by surface-induced spin-density waves. The trends are explained in a magnetic shell model. The magnetic properties of iron cluster show anomalies, suggesting that a high moment to low moment crystallographic phase transition in Fe clusters occurs at relatively low temperatures.

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Thermodynamics of Crystallization in High Polymers. Natural Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3542833 ◽

1955 ◽

Vol 28 (3) ◽

pp. 718-727 ◽

Cited By ~ 3

Author(s):

Donald E. Roberts ◽

Leo Mandelkern

Keyword(s):

Natural Rubber ◽

Melting Temperature ◽

Low Temperatures ◽

Rapid Heating ◽

Heat Of Fusion ◽

Low Molecular Weight ◽

Heating Rates ◽

Equilibrium Melting Temperature ◽

Clapeyron Equation ◽

Melting Temperatures

Abstract The existence of an equilibrium melting temperature, T0m, at 28 ± 1°, for unstretched natural rubber has been established, using dilatometric methods. The lower melting temperatures previously observed are a consequence of the low temperatures of crystallization and the rapid heating rates employed. From melting point studies of mixtures of the polymer with low molecular-weight diluents, the heat of fusion per repeating unit, ΔHu has been evaluated as 15.3 ± 0.5 cal./g. The values of ΔHu and T0m have then been combined with data of other workers to obtain the following information concerning natural rubber: (1) The variation of melting temperature with applied hydrostatic pressure has been calculated from the Clapeyron equation to be 0.0465° C/atm. (2) The degree of erystallinity resulting from maintaining a sample at 0° until the rate of crystallization is negligible has been calculated, by three independent methods, to be in the range 26 to 31 per cent. (3) Analysis of the stress-strain-temperature relationship has indicated that crystallization is the cause of the large internal energy changes that are observed at relatively high elongations.

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