Nonlinearly coupled vibrational modes and self-trapped states: Single-vibron-oscillator case with α-helix parameters
Phys. Rev. B 46, 126 – Published 1 July, 1992
DOI: https://doi.org/10.1103/PhysRevB.46.126
Abstract
Quantum molecular-time-scale generalized-Langevin-equation (MTGLE) theory is applied to calculate spectral linewidths and redshifts of a single vibron oscillator nonlinearly coupled by the Davydov Hamiltonian in the α-helix parameter regime to a chain of linearly coupled molecules. Exact values can also be calculated for this problem. The MTGLE theory gives very accurate results for linewidths and less accurate but acceptable results for redshifts over a wide range of temperatures from 10 to 300 K. These results successfully extend previous calculations carried out in the l-alanine parameter regime to the α-helix parameter regime with a 30-fold increase in frequency of the vibron oscillator and a 1000-fold increase in the square of the nonlinear coupling constant. In constrast to the l-alanine case, the vibron-oscillator frequency is more than 16 times greater than the largest frequency in the phonon manifold.