First-principle investigation on the thermodynamics of X_2N_2O(X = C,Si, Ge) compounds |
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| Affiliation: | 1. Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083, China;2. Department of Mathematics and Physics, Zhengzhou University of Science and Technology, Zhengzhou 450064, China |
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| Abstract: | The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X2N2O (X= C, Si, Ge) compounds are investigated by using the first-principle method. Based on the phonon density of state, the thermodynamic properties of the present compounds are studied under different pressures and at different temperatures. The structural parameters including the bond lengths and bond angles are in agreement with available experimental measurements and theoretical calculations. We employ the elastic theory to calculate the nine independent elastic constants (Cij) and the derived elastic moduli (B, G, E, v). Results indicate that these X2N2O (X= C, Si, Ge) compounds are mechanically stable and show the brittle behaviors. The electronic properties of the present compounds are analyzed by using the band structure and density of states. The phonon dispersion calculations imply that the present compounds are dynamically stable. Based on the quasi-harmonic approximation, the calculations of the specific heat indicate that the temperature in a range of 0 K-1500 K and pressure in a range of 0 GPa-40 GPa have a large effect on the thermal quantities of Ge2N2O, compared with on those of the C2N2O and Si2N2O compounds. |
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| Keywords: | ceramics ab initio calculations crystal structure elastic properties thermodynamic properties |
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