Please see Examples directory for the format of the input file

lr_input
	prefix		’pwscf’
		Sets the prefix for generated and read files. The files 
		generated by the ground state pw.x run should have this 
		same prefix.
	outdir		’./’
		The directory that contains the run critical files, which 
		include the files generated by ground state pw.x run.
	wfcdir		unset
		The directory where the scratch files will be written and read.
		 Restart related files are always written to outdir.
	restart		.false.
		When set to .true., turbo lanczos.x will attempt to restart 
		from a previous interrupted calculation. (see restart_step 
		variable).
	restart_step	itermax
		The code writes restart files every restart step iterations. 
		Restart files are automatically written at the end of itermax
		Lanczos steps.
	lr verbosity	1
		This integer variable controls the amount of information written
		 in standard output.
	disk_io		default
		Fine control of disk usage. Currently only 'reduced' is 
		supported where no restart files are written, apart from the 
		'default' mode.
lr_control
	itermax		500
		Number of iterations to be performed.
	ipol		1
		An integer variable that determines which element of the 
		dynamical polarizabil- ity will be computed: 1 → αxx(ω), 
		2 → αyy(ω), and 3 → αzz(ω). When set to 4, three Lanczos chains
		 are sequentially performed and the full polarizability tensor 
		and the absorption coefficient are computed.
	nipol		1 if ipol < 4; 3 if ipol=4
		Determines the number of zeta coefficients to be calculated for
		 a given polarization direction.
	ltammd		.false.
		When set to .true. the Tamm-Dancoff approximation is used in 
		constructing the Liouvillian.
	no_hxc		.false.
		When set to .true. the change in the internal field (Hartree and
		 exchange-correlation) is ignored in the calculation, resulting
		 in an independent electron approximation.
	charge_response	0
		When set to 1, the code computes the response of the charge 
		density and writes it into a file format determined by the 
		variable plot type. Setting charge response to 1 makes the 
		presence of the card lr post mandatory.
lr_post
	omeg	0.0
		The response of the charge density is calculated for this 
		transition energy (in Rydberg units)
	epsil	0.0
		The broadening/damping term (in Rydberg units).
	beta gamma_z_prefix	’pwscf’
		The prefix of the file where the beta gamma zeta coefficients 
		from the first calculation can be set manually using this 
		parameter. The file outdir/beta gamma z prefix.beta gamma z.x 
		(where x=1-3) must exist.
	w_T_npol	1
		Number of polarization directions considered in the previous 
		calculation. It must be set to 3 if in the previous calculation
		 ipol=4, it must be set to 1 otherwise.
	plot type	1
		An integer variable that determines the format of the file 
		containing the charge density response. 1: A file containing 
		the x y z grid coordinates and the corre- sponding value of the
		 density is produced 2: The density response is written in 
		Xcrysden format 3: The density response is written in the 
		gaussian cube format

