TY - JOUR
T1 - Structural, electronic, phonon and thermodynamic properties of hypothetical type-VIII clathrates Ba8Si46 and Ba8Al 16Si30 investigated by first principles
AU - Norouzzadeh, Payam
AU - Myles, Charles W.
AU - Vashaee, Daryoosh
N1 - Funding Information:
This work was partially supported by AFOSR under Grant No. FA9550-10-1-0010 and the National Science Foundation (NSF) under Grant No. 0933763. The authors would like to thank the Texas Tech and Oklahoma State Universities High Performance Computing Centers for many hours of computing time.
PY - 2014
Y1 - 2014
N2 - We present the results of first principles calculations of the structural, electronic, elastic, vibrational, and thermodynamic properties of the hypothetical silicon-based, guest containing type-VIII clathrates Ba 8Si46 and Ba8Al16Si30. We obtained the lattice constant, formation energy, band structure, density of states, elastic constants, sound velocity, and Debye temperature using the density functional theory with generalized gradient approximation (GGA). We calculated phonon dispersion and vibrational density of states spectra using the density functional perturbation energy within GGA. We computed the temperature dependent specific heat, vibrational entropy, and vibrational Helmholtz free energy by utilizing quasi-harmonic approximation. We found that replacing some silicon atoms in the framework with aluminum atoms leads to the decrease of the fundamental band gap from 1.0 in Ba8Si46 to 0.18 eV in Ba8Al16Si30. Moreover, the guest Ba atoms produced localized phonon modes lying below 1.2, 1.8 THz for Ba 8Si46, and Ba8Al16Si30, respectively, which lead to the reduction of the acoustic bandwidth of the host material. The effect of replacing Si atoms with Al on the properties of the interest is also discussed.
AB - We present the results of first principles calculations of the structural, electronic, elastic, vibrational, and thermodynamic properties of the hypothetical silicon-based, guest containing type-VIII clathrates Ba 8Si46 and Ba8Al16Si30. We obtained the lattice constant, formation energy, band structure, density of states, elastic constants, sound velocity, and Debye temperature using the density functional theory with generalized gradient approximation (GGA). We calculated phonon dispersion and vibrational density of states spectra using the density functional perturbation energy within GGA. We computed the temperature dependent specific heat, vibrational entropy, and vibrational Helmholtz free energy by utilizing quasi-harmonic approximation. We found that replacing some silicon atoms in the framework with aluminum atoms leads to the decrease of the fundamental band gap from 1.0 in Ba8Si46 to 0.18 eV in Ba8Al16Si30. Moreover, the guest Ba atoms produced localized phonon modes lying below 1.2, 1.8 THz for Ba 8Si46, and Ba8Al16Si30, respectively, which lead to the reduction of the acoustic bandwidth of the host material. The effect of replacing Si atoms with Al on the properties of the interest is also discussed.
KW - Density functional theory
KW - Lattice dynamics
KW - Type-VIII clathrate
UR - http://www.scopus.com/inward/record.url?scp=84888101980&partnerID=8YFLogxK
U2 - 10.1016/j.jallcom.2013.10.190
DO - 10.1016/j.jallcom.2013.10.190
M3 - Article
AN - SCOPUS:84888101980
SN - 0925-8388
VL - 587
SP - 474
EP - 480
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
ER -