Calculate phonon dispersion and band structure
Corrected known-answer control: 2H-MoS2 monolayer, a=3.16 A, Mo-S 2.41 A, S-S 3.15 A, 18.5 A vacuum. Mo at (0,0,0.5), S eclipsed at (1/3,2/3,0.5+-0.0716). Replaces 3a42958f, whose Mo sat on the S site (Mo-S 1.575 A).