HESSEMAT

HESSEMAT defines the Hesse matrix in Cartesian coordinates (${\underset{\_}{\mathbf{𝐇}}}^{\mathbf{𝐱}}$ ) for the use in Thermodynamic integration with harmonic reference. For a system containing $N$ atoms, HESSEMAT has $(3N+1)(N+1)$ lines. The first line specifies potential energy $V_{0,\mathbf{𝐱}}({\mathbf{𝐱}}_0)$ (in eV) of the relaxed system for which ${\underset{\_}{\mathbf{𝐇}}}^{\mathbf{𝐱}}$ is computed. The following $3N$ lines are reserved for positions in fractional coordinates of all atoms constituting the system, whereby each line should contain three components of position vector of a single atom.