The Fortran program to implement the differential evolution algorithm to optimize the polynomial model of the vibrational frequency shifts are available from github: https://github.com/kjkwac/diffev

The related publication is as follows:

Kijeong Kwac and Minhaeng Cho, "Differential evolution algorithm for describing vibrational solvatochromism", J. Chem. Phys. 151, 134112 (2019)