Temperature dependence of resistivity of quasi-one-dimensional conductors with nested electronic spectra

1998 ◽  
Vol 57 (11) ◽  
pp. 6204-6207 ◽  
Author(s):  
Lev. P. Gor’kov ◽  
Mogus Mochena
2008 ◽  
Vol 27 (21) ◽  
pp. 5441-5445 ◽  
Author(s):  
Shohei Sase ◽  
Yoen-Seok Cho ◽  
Atsushi Kawachi ◽  
Atsushi Wakamiya ◽  
Shigehiro Yamaguchi ◽  
...  

2014 ◽  
Vol 14 (23) ◽  
pp. 13013-13022 ◽  
Author(s):  
D. M. Murphy

Abstract. A parcel and a one-dimensional model are used to investigate the temperature dependence of ice crystal number density. The number of ice crystals initially formed in a cold cirrus cloud is very sensitive to the nucleation mechanism and the detailed history of cooling rates during nucleation. A possible small spread in the homogeneous freezing threshold due to varying particle composition is identified as a sensitive nucleation parameter. In a parcel model, the slow growth rate of ice crystals at low temperatures inherently leads to a strong increase in ice number density at low temperatures. This temperature dependence is not observed. The model temperature dependence occurs for a wide range of assumptions and for either homogeneous or, less strongly, heterogeneous freezing. However, the parcel model also shows that random temperature fluctuations result in an extremely wide range of ice number densities. A one-dimensional model is used to show that the rare temperature trajectories resulting in the lowest number densities are disproportionately important. Low number density ice crystals sediment and influence a large volume of air. When such fall streaks are included, the ice number becomes less sensitive to the details of nucleation than it is in a parcel model. The one-dimensional simulations have a more realistic temperature dependence than the parcel mode. The one-dimensional model also produces layers with vertical dimensions of meters even if the temperature forcing has a much broader vertical wavelength. Unlike warm clouds, cirrus clouds are frequently surrounded by supersaturated air. Sedimentation through supersaturated air increases the importance of any process that produces small numbers of ice crystals. This paper emphasizes the relatively rare temperature trajectories that produce the fewest crystals. Other processes are heterogeneous nucleation, sedimentation from the very bottom of clouds, annealing of disordered to hexagonal ice, and entrainment.


1961 ◽  
Vol 39 (12) ◽  
pp. 1733-1737 ◽  
Author(s):  
Y. Y. Lee

The adequacy of the approximation method used by McMillan and Opechowski in their theoretical study of the temperature dependence of the paramagnetic resonance line shape function is very difficult to ascertain for the case of a typical paramagnetic crystal. For this reason the approximation method has been investigated for the very simple case of the one-dimensional Ising model. Exact expressions for the line shape function of the model are compared with expressions obtained by the approximation method mentioned above. The agreement between the two expressions is found to be very good in general, and extremely good at very low temperatures.


2002 ◽  
Vol 63 (1-3) ◽  
pp. 87-90
Author(s):  
N Mori ◽  
C Hamaguchi ◽  
L Eaves ◽  
P.C Main

1970 ◽  
Vol 14 ◽  
pp. 433-440
Author(s):  
W. S. McCain ◽  
D. L. Albright ◽  
W. O. J. Boo

AbstractLattice constants were measured as a function of temperature by single crystal diffracrometry in the temperature range which includes the Néel temperature of VF2(TN= 7°K). The lattice constants of VF2(D4h14=P42m n m) were measured from room temperature down to 4.2°K. In this range rhe tetragonal c-axis contracts 0.58% from 3.2359 Å (RT) to 3.2170 Å (4.2°K). On the other hand, the a-axes show a net expansion of 0.18% from 4.8023 Å (RT) to 4.8110 Å at 4.2°K. The temperature dependence of the lattice constants can be correlated with anisotropy of exchange forces. Vanadium Ions occupy the center and corner positions of the unit cell. Strong magnetic interactions are directed parallel to the c-axis >001< with considerably weaker interactions parallel to the body diagonals >111< The relative strengths of the two exchange integrals are J >001< = 50 J >111<. As a consequence the magnetic ordering is one-dîmensional along the c-axis and the associated distortions arise from the strong magnetic interactions along this axis.


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