  Defects such as vacancies and impurities could have profound effects on the
transport properties of thermoelectric materials. However, it is usually quite
difficult to directly calculate the thermoelectric properties of
defect-containing systems via first-principles method since very large
supercell is required. In this work, based on the linear response theory and
the kernel polynomial method, we present an efficient approach that can help to
calculate the thermoelectric transport coefficients of a large system
containing millions of atoms at arbitrary chemical potential and temperature.
As a prototype example, we consider dilute vacancies and hydrogen impurities in
a large scale {\gamma}-graphyne sheet and discuss their effects on the
thermoelectric transport properties.
