文摘
The crystal structure of hexaphenyldisilane, Si2(C6H5)6, was determined from synchrotron powder diffraction data. The compound crystallizes in orthorhombic space group P212121 with the following unit cell dimensions: a = 20.2889(8) 脜, b = 16.9602(7) 脜, and c = 8.5506(4) 脜. Second-harmonic generation measurements as well as density functional theory calculations were used to confirm the structure determination. The combination of experimental and theoretical studies yields a Si鈥揝i distance [d(Si鈥揝i)] of 2.38 脜. The phenyl rings of a molecule are staggered and slightly distorted, so that the molecule is acentric. Thermodynamic measurements showed no phase transition in the temperature range of 2鈥?00 K. The molar heat capacity (Cp) at 298.15 K of 604(6) J mol鈥? K鈥? was established experimentally and by lattice dynamic calculations. The molar entropy (S掳) and the molar enthalpy (螖H) in the temperature range of 0鈥?98.15 K are 674(7) J mol鈥? K鈥? and 97(6) kJ mol鈥? respectiveley. The Debye temperature (胃D) is 207(5) K. The thermal expansion of Si2(C6H5)6 is strongly anisotropic, and negative in two directions as determined via temperature-dependent X-ray powder diffraction experiments. The linear thermal expansion coefficients at 298.15 K are as follows: 伪a = 鈭?(2) 脳 10鈥? K鈥?, 伪b = 鈭?(2) 脳 10鈥? K鈥?, and 伪c = 2.21(4) 脳 10鈥? K鈥?. The volumetric thermal expansion coefficient (伪V) at 298.15 K is 2.13(5) 脳 10鈥? K鈥?.