Advances in Condensed Matter Physics / 2019 / Article / Tab 2

Review Article

Survey of the Thermodynamic Properties of the Charge Density Wave Systems

Table 2

Materials (2D CDW) transition metal dichalcogenides 2H-NbSe2, TiSe2, 2H-TaSe2, and 2H-TaS2. Molar volumes are given in cm3, specific heat discontinuities in J/molK, thermal expansion discontinuities in K−1, elastic velocity discontinuities in , and measured and calculated elastic constants in GPa. Discrepancies exist among the experimental values of the Young modulus; the largest values are only indicated. Ratio = calculated /experimental elastic constant.

Materials Molar volume
cm3
TCDW
K
Specific heat

J/molK
Thermal expansion
coefficient
α
K−1
Elastic velocity decrease
∆V/V
Elastic constant
GPa
calculated

GPa
Ratio

2H-NbSe240300.5 [19] axis
-3x10−6 [19]
axis
-2x10−7 [18]
axis
-5x10−4 [16, 17]
C11=108 [17]
C33=460
35~0.3

TiSe239.62001.15 [22]
0.5 [23]
axis
-2.5x10−6 [19]
along the axis
-0.05 [19]
axis
C11~ 190 [20]
1800
800
~10
~4

2H-TaSe21204
[24]
axis
-8x10−6 [25]
axis
-0.0005
[16, 17]
Young modulus ( axis)
[16]
16~0.1

2H-TaS235.7782.8
[24]
no discountin.

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