Molecules with Elk

[Stefano]

Hello,

I am trying to use elk with small molecules.
This is how my input file looks like (for H2)

tasks
  0

lorbcnd
 .true.

!molecule calculation (atomic positions are in Cartesian coordinates)
molecule
 .true.

! put molecule in a large box
avec
 6.0 0.0 0.0
 0.0 6.0 0.0
 0.0 0.0 6.0

rgkmax
 4.0

autormt
 .true.

!gmaxvr
! 14.0

sppath
  '../../species/'

! atomic positions in Cartesian coordinates
atoms
  1                                     : nspecies
 'H.in'                                 : spfname
  2                                     : natoms
  0.0   0.0   0.0    0.0  0.0  0.0      : atpos, bfcmt
  1.4   0.0   0.0    0.0  0.0  0.0

But I get the following warnings:

Elk code version 2.3.22 started

Info(readinput): variable 'autormt' is no longer used

Info(main): several copies of Elk may be running in this path
(this could be intentional, or result from a previous crash,
 or arise from an incorrect MPI compilation)

Info(main): current task :      0
Info(checkmt): reduced muffin-tin radius of species   1 (H) from   1.4000 to   0.6750
Info(findsymcrys): atomic basis shift (lattice) :
  0.3833333333       0.000000000       0.000000000
See GEOMETRY.OUT for new atomic positions

Warning(linengy): could not find   1 linearisation energies in s.c. loop     1
Warning(linengy): could not find   1 linearisation energies in s.c. loop     2
Warning(linengy): could not find   1 linearisation energies in s.c. loop     3
...
Warning(linengy): could not find   1 linearisation energies in s.c. loop    18
Warning(linengy): could not find   1 linearisation energies in s.c. loop    19

But the energy seems converged

-1.36344888016    
-1.34162070674    
-1.31375165904    
-1.28486991711    
-1.25948881878    
-1.24035643218    
-1.22803030167    
-1.22133001228    
-1.21834295627    
-1.21732425829    
-1.21710197041    
-1.21713267738    
-1.21721144709    
-1.21727476083    
-1.21731180276    
-1.21732929729    
-1.21733612638    
-1.21733832228    
-1.21733880802

I have the same warning with others molecules also.

Moreover for NH3 I get also the following warning

Warning(rhonorm): total charge density incorrect for s.c. loop     1
 Calculated :    9.910160955    
 Required   :    10.00000000

What the problem is? How should I set the input parameters for a correct treatment of molecules? Some hints?

Thanks

Stefano

[Sangeeta Sharma]

Your H atoms are too close. Please try putting the second atom at 2.4 rather than 1.4 atomic units.

Please use the latest version of the code. Also autormt is not is use anymore. Please remove the variable autormt from elk.in.

[Stefano]

Thanks for the suggestions

[J. K. Dewhurst]

Hi Stefano,

You are much better off using a quantum chemistry code for studying molecules. LAPW is just too inefficient for finite systems in a large box: its strength is solids.

Regards,
Kay.