DFT Modeling of L-Lactide Decamer Structure and Raman Spectrum with Electron Density Functionals of Hybrid and GGA Type

Sixteen approximations of the density functional theory for calculating the structure and Raman spectra of the most stable α-phase of poly(L-lactide) (PLLA) with an orthorhombic crystalline lattice have been analyzed. It is shown that the GGA functionals OLYP and PBE provide good correspondence with experimental X-ray diffraction and Raman spectroscopy data. It is found that, when using extended basis sets of three- and four-exponential types, the choice of the functional affects the calculation results much more radically than the choice of the basis set.