# FINDIF

Performs finite difference computations of energy derivative, with respect to nuclear displacements for geometry optimizations and vibrational frequency analyses, where the required analytical derivatives are not available.

## General

### DISP_SIZE

> Displacement size in au for finite-differences.

> - Type: double
> - Default: 0.005

### FD_PROJECT

> Do discount rotational degrees of freedom in a finite difference frequency calculation. Turned off at non-stationary geometries and in the presence of external perturbations.

> - Type: boolean
> - Default: true

### GRADIENT_WRITE

> Do write a gradient output file? If so, the filename will end in .grad, and the prefix is determined by WRITER_FILE_LABEL (if set), or else by the name of the output file plus the name of the current molecule.

> - Type: boolean
> - Default: false

### HESSIAN_WRITE

> Do write a hessian output file? If so, the filename will end in .hess, and the prefix is determined by WRITER_FILE_LABEL (if set), or else by the name of the output file plus the name of the current molecule.

> - Type: boolean
> - Default: false

### NORMAL_MODES_WRITE

> Do write a file containing the normal modes in Molden format? If so, the filename will end in .molden_normal_modes, and the prefix is determined by WRITER_FILE_LABEL (if set), or else by the name of the output file plus the name of the current molecule.

> - Type: boolean
> - Default: false

### POINTS

> Number of points for finite-differences (3 or 5)

> - Type: integer
> - Default: 3