Phonon Calculation Sample Clauses

Phonon Calculation. ‌ Phonons are of fundamental importance for studying material properties at quantum mechanical level (see Section 2.1.8). Applying the ML force calculation into the phonon calculations, we have to technically deal with numerical problems, as for all the represent- ing configurations, internal vectors can be close to zeros in this case. Vector ‘flipping’ typically happens and brings into disruptive discontinuity by the sudden rotations of some small representing vectors. This problem was addressed and can be found in detail in Section 5.4. 12 Frequency (THz) 10 8 6 4 0 Γ X W X K Γ L SW DFTB MLOTF σerr = 0.05 MLOTF σerr = 0.001 × × Figure 6.7: Comparison of the phonon spectra calculated by MLOTF (red, a=5.474 A˚) and DFTB(blue, relaxed lattice constant a=5.474 ˚A), SW(black, a=5.44 ˚A). MLOTF phonon were calculated using σerror = 5 10−4 and 1 10−3 eV/˚A. For the MLOTF calculation, database was 200 configuration generated from MD trajec- tory of Si at 300K. In phonon calculations, σerror can be optimised by calculation at the Γ points.