Boson Fields Near Melting Transition

ABSTRACTOne to three layer cyclohexane films confined between mica-like surfaces are studied to elucidate changes in the films' lattice-type. The laterally confined film is in equilibrium with the bulk fluid that is well into the liquid regime of its phase diagram. Monte Carlo simulations are conducted at constant chemical potential, temperature, and V=Ah, where A is the lateral area and h is the separation between the walls. One and two layers of fluid freeze as h increases. The one layer fluid has a triangular lattice, while the two layer fluid exhibits first a square lattice and then a triangular lattice with increasing surface separation. In contrast to previous studies, solidlike order is induced primarily by the strong fluid-solid interaction and is largely a function of pore width. A shift in the relative alignment of the surfaces perturbs the solidlike fluid structure but does not cause the sudden shear melting transition associated with epitaxial alignment of the fluid atoms with the surface. There is a correlation between the shear stress calculated in the computer experiments and that measured in Surface Forces Apparatus experiments.

Download Full-text

Lead inclusions in aluminium

MRS Proceedings ◽

10.1557/proc-157-247 ◽

1989 ◽

Vol 157 ◽

Cited By ~ 6

Author(s):

E. Johnson ◽

L. Gråbaek ◽

J. Bohr ◽

A. Johansen ◽

L. Sarholt-Kristensen ◽

...

Keyword(s):

Hysteresis Loop ◽

Room Temperature ◽

Noble Gas ◽

Melting Transition ◽

X Ray Diffraction ◽

Free Surfaces ◽

The Matrix ◽

Mean Size ◽

The Mean ◽

Spontaneous Phase

ABSTRACTIon implantation at room temperature of lead into aluminium leads to spontaneous phase separation and formation of lead precipitates growing topotactically with the matrix. Unlike the highly pressurised (∼ 1–5 GPa) solid inclusions formed after noble gas implantations, the pressure in the lead precipitates is found to be less than 0.12 GPa.Recently we have observed the intriguing result that the lead inclusions in aluminium exhibit both superheating and supercooling [1]. In this paper we review and elaborate on these results. Small implantation-induced lead precipitates embedded in an aluminium matrix were studied by X-ray diffraction. The (111) Bragg peak originating from the lead crystals was followed during several temperature cycles, from room temperature to 678 K. The melting temperature for bulk lead is 601 K. In the first heating cycle we found a superheating of the lead precipitates of 67 K before melting occurred. During subsequent cooling a supercooling of 21 K below the solidification point of bulk lead was observed. In the subsequent heating cycles this hysteresis at the melting transition was reproducible. The full width of the hysteresis loop slowly decreased to 62 K, while the mean size of the inclusions gradually increased from 14.5 nm to 27 nm. The phenomena of superheating and supercooling are thus most pronounced for the small crystallites. The persistence of the hysteresis loop over successive heating cycles demonstrate that its cause is intrinsic in nature, and it is believed that the superheating originates from the lack of free surfaces of the lead inclusions.

Download Full-text

A Rarita-Schwinger formalism for boson fields

Il Nuovo Cimento A ◽

10.1007/bf02754280 ◽

1970 ◽

Vol 68 (1) ◽

pp. 89-104 ◽

Cited By ~ 1

Author(s):

M. L. Nack

Keyword(s):

Boson Fields

Download Full-text

Melting of Aromatic Compounds: Molecular Dynamics Simulations

MRS Proceedings ◽

10.1557/proc-408-327 ◽

1995 ◽

Vol 408 ◽

Author(s):

P. W.-C. Kung ◽

J. T. Books ◽

C. M. Freeman ◽

S. M. Levine ◽

B. Vessali ◽

...

Keyword(s):

Molecular Dynamics ◽

Molecular Crystal ◽

Constant Pressure ◽

Molecular Crystals ◽

Melting Transition ◽

Melting Temperatures ◽

Molecular Dynamics Calculations ◽

Dynamics Simulations ◽

Experimental Melting Point ◽

Experimental Melting

AbstractWe have used constant pressure molecular dynamics calculations to explore the behavior at various temperatures of two molecular crystals: benzene and a brominated phenyl compound. We observed a melting transition by heating the crystals from a low temperature. In the case of benzene, we performed one heating run of about 1 ns and obtained agreement with the experimental melting point to within some 8%. We have also simulated the melting of a more complex molecular crystal that contains bromine and phenyl groups. We performed four heating runs, with different rates of heating. For total simulation times of about 100, 220, 770, and 1 I50ps, the heating runs predicted melting temperatures that differed from the experimental melting temperature by 53%, 33%, 25%, and 9% respectively.

Download Full-text