**Purpose of d3hess.x:**
This is a post processing program to compute second derivatives of D3 dispersion in QE.
The d3hess.x program should be run after an scf or relax calculation.
It reads the molecular geometry from the xml file in the outdir and save
the second derivatives matrix in a file on the disk.
Afterwords, phonon reads the file and add the D3 Hessian matrix to the dynamical matrix with the proper phase (q),
to include dispersion effects on vibrational frequencies.
The workflow is just:
(1) do an SCF
(2) run d3hess
(3) run phonon
Please note that filhess in d3hess input and dftd3_hess in phonon input, if given, should match.
**Structure of the input data:**
============================
**&INPUT**
...
**/**