Solid thorium silicides

2 Silicon compounds and complexes XI.2.1 Solid thorium silicides 

There are four well-established intermetallic phases in this system, Th3Si2, ThSi, ThsSis and ThSi2. The structural data on these compounds have been assembled by [1981CHI/AKH] and are shown in Table XI-8. In addition Brown and Norreys [1960BRO/NOR] found evidence for a phase of composition TheSin, with two polymorphs with a transition temperature of ca. 1573 K. The structural data in Table XI-8 suggest that they are defect structures of ThSi2. 

Phase Symmetry, Space Group Structural type Lattice parameters (A) 

Given the ambiguity in the data, the following values, valid for 1685 to 1961 K, are given for information only. 

The value of the enthalpy of formation of ThSi2(er), -165.3 kJ mol from these high temperature measurements (ca. 1750 K) supports the eonsistent ealorimetrie values determined near room temperature, noted above. The seleeted value is the weighted mean of the two ealorimetrie values  

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