!=========================================================================!
!		            README.WANNIER				  !
!					Author: Manu Sharma	          !
!					msharma@alumni.Princeton.EDU	  !
!=========================================================================!
!                       INPUT FORMAT FOR WFDD.X                           !
!=========================================================================!
! This code was originally written by Yudong Wu and later modified by     !
! Manu Sharma. This is intended to be a post-processing code and the      !
! search for the appropriate Unitary transformation can be done using not !
! only damped-dynamics, but  also Steepest descent and conjugate gradient !
! algorithms. The advantage                                               !
! is that SD/CG can serve as benchmarks to make sure that the DD is       !
! converging to the correct values (in deciding the parameters Q and DT   !
! for the DD). The disadvantage is that SD/CG schemes are slower than     !
! the DD. It is useful however, before using DD in production runs, to    !
! make sure that the parameters (Q and DT) give the same answer as the SD !
! or CG. This code requires as input, the overlap matrix. This can be     !
! calculated from the CP code by setting CALWF to 2 in the &WANNIER       !
! namelist (The default value is 3, for Wannier dynamics. This option     !
! outputs the overlap matrix to unit 38, and wfdd.x reads it from the same!
! file.  								  !
! In addition to that, you need an input file of the following form.      !
!									  !
!									  !
! 1       0.3    0.5    100  10       CGORDD  WFDT MAXWFDT  NIT  NSD      !    
! 1500 5.0  0.3 .true.  100  1.0d-8   Q   DT   FRIC  ADAPT  NSTEPS   TOLW !
! .true.                              RESTART				  !
!									  !
! CGORDD : Whether to do SD/CG optimization of damped dynamics            !
!          Can take the values 1 or 2. 1 means SD/CG and 2 means DD       !
! WFDT   : Used when GCORDD=1. This is the step length you take in the    !
!          direction of steepest descent.                                 !
! MAXWFDT: Used when CGORDD=1. This is the maximum step length you take   !
!          in the direction if steepest descent. if WFDT or MAXWFDT are   !
!          large, the calculation will not converge. The code uses the    !
!          parabolic approximation to estimate the appropriate step length!
!          and if it is less than WFDT, then WFDT is taken as the step    !
!          length and if more than MAXWFDT then MAXWFDT is taken as the   !
!          Step length.                                                   !
! NIT    : Used when CGORDD=1. This is the maxumum number of iterations   !
!          to do.							  !
! NSD    : Used whdn CGORDD=1. This is the number of Steepest descent     !
!          steps to do. If NSD = NIT then it is a pure SD optimization    !
!          If NSD < NIT, then the code first does NSD Steepest descent    !
!          steps and then NIT-NSD Conjugate gradient steps.               !
! RESTART: Use this option to continue a SD/CG/DD optimization. This      !
!          option reads the Unitray transform from fort.39, written at the!
!          end of the last run and continues from there.                  !
!									  !
! The other  are used for the Damped dynamics and are  defined            !
! in the INPUT_CP.* file in the Doc/ directory under NAMELIST &WANNIER.     !
!								  	  !
! The program may be compiled by make wfdd.x and then run as follows      !
!       ./wfdd.x < [input-filename] > [output-filename] &                 !
! The output file will contain the inverse spread (which is the functional!
! that is actually maximized in the code rather than minimizing the       !
! spread) at each step of the optimization.                               !
!  									  !
!                                                      Manu Sharma        !
!                                                      February 14th,2006 !
!=========================================================================!
!      COPYRIGHT MANU SHARMA/YUDONG WU/NICOLA MARZARI/ROBERTO CAR	  !
!=========================================================================!
