TY  - JOUR
AU  - Ligatchev, Valeri
PY  - 2025
DA  - 2025/05/22
TI  - Quantitative Evaluations on Harmonic and Anharmonic Lattice Thermal Capacity of Polymers
JO  - Recent Progress in Materials
SP  - 008
VL  - 07
IS  - 02
AB  - So-called ‘Generalized Skettrup Model(s)’ (GSMs) of different (1D, 2D, 3D) spatial dimensionalities are used at simulations on temperature-dependent harmonic and anharmonic fractions of lattice thermal capacity of polyethylene and polypropylene with crystalline and/or amorphous atomic structures of limited spatial extents. Basic equations of the GSM slot in explicitly quantization effects of the single-particle and many-particle energy levels of spatially confined phonons. The harmonic lattice thermal capacity of 1D and 3D polymers is evaluated entirely based on single-particle (fundamental) states of the confined LA, TA, and optical phonons. Statistical characteristics of many-particle states of the LA and TA phonons are obtained based on the concept of many-particle vibrational density-of-states, introduced in 1995. Those characteristics define features of temperature-dependent anharmonic lattice capacities of 1D, 2D and 3D versions of the GSM in an essentially ‘non-perturbative’ manner. Anisotropic effects in 3D crystalline polymers are incorporated via evaluation of anisotropic sound velocities of conventional thermal waves confined within 3D crystalline fragments of those polymers. Such evaluations have been carried out quantitatively for orthorhombic 3D polyethylene via implementation of the Christoffel Matrix formalism. Simulated temperature-dependent lattice thermal capacities are compared with their experimental counterpart for polyethylene and polypropylene, as well as with predictions of Tarasov’s Equations and those of the ‘three-band’ model.
SN  - 2689-5846
UR  - https://doi.org/10.21926/rpm.2502008
DO  - 10.21926/rpm.2502008
ID  - Ligatchev2025
ER  -