Fig. 1. Lattice thermal conductivities and phonon mode lattice thermal conductivities of LiGaS₂ and Li₂BaSnS₄. (a) Temperature-dependent lattice thermal conductivities of LiGaS₂ and Li₂BaSnS₄ along a, b, and c axis; (b) frequency-dependent phonon mode contribution to the lattice thermal conductivities of LiGaS₂ and Li₂BaSnS₄ along c axis at room temperature (300 K)

Fig. 2. Phonon dispersion and phonon density of states. (a) Li₂BaSnS₄; (b) LiGaS₂

Fig. 3. Outer group product of group velocities of Li₂BaSnS₄ and LiGaS₂ in frequency domain

Fig. 4. Analysis of strength of bonds of Li₂BaSnS₄ and LiGaS₂. (a) Distribution of electron localization function in plane(01-0) of Li₂BaSnS₂; (b) distribution of electron localization function in plane (010) of LiGaS₂; (c) crystal orbital Hamilton population of Sn-S and Ga-S

Fig. 5. Crystal structures. (a) Li₂BaSnS₄; (b) LiGaS₂

Fig. 6. Phonon lifetime. (a) Phonon lifetime of Li₂BaSnS₄ and LiGaS₂; (b) phonon lifetime of normal progress and umklapp progress of LiGaS₂; (c) phonon lifetime of normal progress and umklapp progress of Li₂BaSnS₄

Fig. 7. Phonon anharmonic properties of Li₂BaSnS₄ and LiGaS₂. (a) Mode Grüneisen parameters of Li₂BaSnS₄ and LiGaS₂ in frequency domain; (b) weighted joint density of states of Li₂BaSnS₄ and LiGaS₂

Table 1. Contributions of TA₁, TA₂, LA phonons, low-frequency optical phonons, and other optical phonons to total lattice thermal conductivities of LiGaS₂ and Li₂BaS