#Ultra low thermal conductivity of quasi 1D bulk material $\beta-Bi_4 I_4$ The thermal transportation properties of recently synthesized quasi-1D bulk $\beta-Bi_4 I_4$ is explored from first principle. The thermal conductivity of this system is found rather low because of the phonon localization caused by the low-dimension nature and large anharmonic scattering of phonons. Detailed analysis of lattice dynamic calculation is applied to explain the origin of the anharmonic effects. The Seebeck coefficients and electric conductance are calculated from first principle and then ZT value is given. We found $\beta-Bi_4 I_4$ is actually potential for the application of thermoelectric. This research could be a guidance for further exploring of advanced low thermal conductivity materials.

keywords:Thermal conductivity, quasi-1D,$\beta-Bi_4 I_4$, thermoelectric, phonons

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