TY - JOUR

T1 - "First-principles Analysis of the Vibrational Properties of the Type II SiGe Alloy Clathrates",

AU - Xue, Dong

AU - Myles, Charles

PY - 2019/5/10

Y1 - 2019/5/10

N2 - We have mostly performed vibrational studies of Type-II silicon-germanium clathrate
alloys, namely, Si136-xGex (0 < x < 128), using periodic density functional theory (DFT). Our computed
lattice constant for various stoichiometric amount, namely, x, of Ge agrees to some extent with
the observed X-ray diraction (XRD) data, along with monotonically increasing dependence on x.
According to our bandgap energy calculation via Vienna ab initio simulation package (VASP), Si128Ge8
has a “nearly-direct” bandgap of approximately 1.27 eV, which agrees well with the previously
calculated result (~1.23 eV), which was obtained using the Cambridge sequential simulation total
energy package (CASTEP). Most of our first-principles calculations focus on exploring the low-energy
transverse acoustic (TA) phonons that contribute dominantly to the induction of negative thermal
expansion (NTE) behavior. Moreover, our work has predicted that the Si104Ge32 framework exhibits
NTE in the temperature range of 3–8

AB - We have mostly performed vibrational studies of Type-II silicon-germanium clathrate
alloys, namely, Si136-xGex (0 < x < 128), using periodic density functional theory (DFT). Our computed
lattice constant for various stoichiometric amount, namely, x, of Ge agrees to some extent with
the observed X-ray diraction (XRD) data, along with monotonically increasing dependence on x.
According to our bandgap energy calculation via Vienna ab initio simulation package (VASP), Si128Ge8
has a “nearly-direct” bandgap of approximately 1.27 eV, which agrees well with the previously
calculated result (~1.23 eV), which was obtained using the Cambridge sequential simulation total
energy package (CASTEP). Most of our first-principles calculations focus on exploring the low-energy
transverse acoustic (TA) phonons that contribute dominantly to the induction of negative thermal
expansion (NTE) behavior. Moreover, our work has predicted that the Si104Ge32 framework exhibits
NTE in the temperature range of 3–8

M3 - Article

SP - 723

EP - 749

JO - Nanomaterials

JF - Nanomaterials

ER -