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= bdfopt =


<<TableOfContents(4)>>

Geometry optimiser of BDF package.  Two optimizers can be used:

1. Interface to DL-FIND. For details, see: http://ccpforge.cse.rl.ac.uk/gf/project/dl-find/

"DL-FIND: An Open-Source Geometry Optimizer for Atomistic Simulations", Johannes Kästner, Joanne M. Carr, Thomas W. Keal, Walter Thiel, Adrian Wander and Paul Sherwood, J. Phys. Chem. A, 2009, 113 (43), 11856-11865. DOI: 10.1021/jp9028968
 
2. Original optimizer in BDF developed by Dr. Yong Zhang.

This BDFOPT module can be used to find minimal points, saddle points and also conical intersection points, when combined with TD-DFT and RESP modules.
For details of the interface, see '''bdfopt/''', '''module/bdfopt_mod.F90,dlfind_module.F90''', '''sys_util/bdf_dlfind_util.F90''' for interface.

== Current limitations ==

1. Change of symmetry during optimization is not correctly handled for excited state optimization, because the correct input file needs to be prepared.

== Examples ==

=== Ground-state opt ===

{{{

$COMPASS    
Title
 CH2 Molecule test run, cc-pvqz
Basis
 3-21g
# cc-pvdz
Geometry
O       0.00000000     -0.00000000      0.00174418
H      -0.78045951      0.00000000     -0.10962269
H       0.78045951      0.00000000     -0.10962269
End geometry
Check
Skeleton
$END

$bdfopt
$end

$XUANYUAN
$END

$SCF
RHF
$END

$resp
geom
norder
1
method
1
$end

}}}

=== Excited state opt ===

{{{

$COMPASS    
Title
 CH2 Molecule test run, cc-pvqz
Basis
 3-21g
Geometry
 O  0.000000    0.000000    0.243991
 H  0.000000    1.178727   -0.45964
 H  0.000000   -1.178727   -0.45964
End geometry
Check
Skeleton
$END

$bdfopt
$end

$XUANYUAN
$END

$SCF
RHF
$END

$tddft
imethod
1
itda
0
idiag
1
istore
1
iexit
1
crit_e
1.d-8
crit_vec
1.d-6
$end

$resp
geom
norder
1
method
2
states
1
1 4 1
nfiles
1
$end

}}}

== General keywords ==
=== IPRT ===

=== SOLVER ===
=0, DLFIND; =1, BDF optimizer

=== MAXCYCLE ===

=== TOLGRAD ===

=== TOLENE ===

=== IOPT ===
Algorithm for optimization, default L-BFGS

=== ICOORD ===
Coordinates

=== IMULTI ===
multi-state optimization for conical intersection

=== ILINE ===
line search