Molecular Dynamics Simulation on Terahertz Spectra of Methamphetamine Hydrochloride

Abstract

Methamphetamine hydrochloride crystal (trade name Methedrine) that is one of the illegal drugs used as a stimulant to the nervous system has been considered to be detected by T-ray via the terahertz time-domain spectroscopy (THz-TDS). In this research, we simulated the THz spectra of Methedrine by molecular dynamics methods for the first time. The terahertz spectra at temperatures 78.4K, 200K, 294K and 400K in the frequency range of 10-100cm-1 were investigated, which exhibited the variation of spectra position and intensity with increasing temperature. Firstly, we used DL_POLY simulation package to obtain the instantaneous values of the dipole moment. Subsequently, the intensities of THz vibrational modes were obtained by the Fourier transform of the autocorrelation function of the dipole moment. The results showed our theoretical calculation by molecular dynamics simulations got a good consistency with available experimental spectroscopy. These are useful to determine the best conditions of temperature at which the terahertz time-domain spectroscopy of Methedrine results a highly informative spectrum.