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An investigation on electronic, elastic and thermodynamic properties of VN under high pressure has been conducted using first-principles calculations based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. At elevated pressures VN is predicted to undergo a structural phase transition from the relatively open NaCl-type structure into the denser CsCl-type atomic arrangement. The predicted transition pressure is 189 GPa. The elastic constants, Debye temperature as a function of pressure and temperature of VN are presented.

We investigate the electronic, dynamic and thermodynamic properties of α-MnO2 using first-principles calculations based on density functional theory (DFT) with the GGA+U method. The results of electronic structures show that α-MnO2is a semiconductor with a direct band gap of 1.4 eV at Γ point. The results of dynamic properties indicate that the structure of α-MnO2 is dynamically unstable at ground-state. Several important thermodynamic quantities, such as entropy, enthalpy and Gibbs free energy, et al each as a function of temperature were presented.

In situ electrical resistivity measurement of powdered CdTe has been performed under high pressure using a diamond anvil cell equipped with a microcircuit. With the pressure increasing from 2.7 to 3.8 GPa, a sharp decrease in resistivity of over three orders of magnitude is observed. This is due to the appearance of rock-salt CdTe. At about 6.5 GPa a resistivity inflexion appears which has not been reported before. It is caused by the obvious decrease of band gap in certain symmetry directions of the Brillouin zone of rock-salt CdTe. From 6.5 to 10 GPa, the descending trend of the resistivity turns gently. At about 10 GPa, a cusp corresponding to the transition to the Cmcm phase is distinguished. Between 10 and 38 GPa, three leap points have been detected at 15.5 GPa, 22.2 GPa and 30 GPa, which imply abundant electronic phase transitions of CdTe. Resistivity measurements were also performed in a wide temperature range from liquid nitrogen temperature (77 K) to 450 K. It is proved that rock-salt CdTe does not show a typical metallic transport character. In the pressure range of 6.0–7.0 GPa, CdTe has a band gap of about 445 meV. The relationship of lnρ to 1/T is also fitted linearly to yield the ionization energy of impurities at different pressures.