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Sergey Yurchenko edited this page Nov 1, 2022 · 8 revisions

The Duo input files for this example can be found in Duo Tutorial

See The ab initio ground-state potential energy function of beryllium monohydride, BeH by Jacek Koput, JCP 135, 244308 (2011)

The ground electronic state of BeH is a doublet (2Sigma+), see https://www.ucl.ac.uk/~ucapsy0/diatomics.html.

Energy calculations

In order to solve the nuclear motion Schroediner equation to compute ro-vibronic spectra of BeH with Duo we need to prepare an input file using the following structure (BeH_Koput_01.inp):

 atoms Be H
 (Total number of states taken into account)
 nstates 1
 
 (Total angular momentum quantum  - a value or an interval)
 jrot 0.5 - 2.5 
 
 (Defining the integration grid)
 grid
   npoints 501
   range   0.4 8.0
   type 0 
 end
 
 CONTRACTION
  vib
  vmax  30
 END


 poten 1
 units cm-1 angstroms
 name 'X2Sigma+'
 lambda 0
 symmetry +
 mult   2
 type grid
 values   
 0.60     105169.63
 0.65      77543.34
 0.70      55670.88
 0.75      38357.64
 0.80      24675.42
 0.85      13896.77
 0.90       5447.96
 0.95      -1125.87
 1.00      -6186.94
 1.05     -10024.96
 1.10     -12872.63
 1.15     -14917.62
 1.20     -16311.92
 1.25     -17179.13
 1.30     -17620.16
 1.32     -17696.29
 1.33     -17715.26
 1.34     -17722.22
 1.35     -17717.69
 1.36     -17702.19
 1.37     -17676.19
 1.38     -17640.16
 1.40     -17539.76
 1.45     -17142.53
 1.50     -16572.59
 1.55     -15868.72
 1.60     -15063.34
 1.65     -14183.71
 1.70     -13252.86
 1.80       -11313.
 1.90      -9369.74
 2.00      -7518.32
 2.10      -5832.29
 2.20      -4366.71
 2.30      -3155.94
 2.40      -2208.98
 2.50      -1507.72
 2.60      -1013.23
 2.80       -456.87
 3.00       -221.85
 3.50        -72.13
 4.00        -41.65
 4.50         -24.9
 5.00        -14.32
 6.00         -4.74
 8.00         -0.75
 10.00        -0.19
 20.00          0.0
end

where we use the potential energy curve (PEC) defined in Table III of Koput (2011) in a grid form.

An alternative definition is an analytical PEC, see e.g. ExoMol-SiO (All ExoMol papers can be download from https://www.ucl.ac.uk/~ucapsy0/publications.html), BeH_Koput_02.inp

 poten 1
 units cm-1 angstroms
 name 'X2Sigma+'
 lambda 0
 symmetry +
 mult   2
 type ЕМО
 values   
 V0             0.00
 RE             1.342394
 DE            17590.00
 RREF         -1.00000000
 PL            3.00000000
 PR            3.00000000
 NL            0.00000000
 NR            0.00000000
 b0            1.8400002 
end  

Refinement

This PEC can be refined by fitting to experimental energies using the following input structure (BeH_Koput_03.inp):

poten 1
name 'X2Sigma+'
lambda 0
symmetry +
mult   2
type    EMO
Values
V0             0.00
RE             1.342394
DE            17590.00   fit
RREF         -1.00000000
PL            3.00000000
PR            3.00000000
NL            0.00000000
NR            0.00000000
b0            1.8450002    fit
end    


FITTING
JLIST    0.5 - 0.5
itmax 12
fit_factor  1e5
output   BeH_01
lock     1000 
robust  0.0001
energies                  ( state   v     ilambda isigma omega    weight  comment <-  state v ilambda isigma  weigh
 0.5  +       1           0       1       0       0     0.5     0.5    1.00
 0.5  +       2    1986.416       1       1       0     0.5     0.5    1.00
 0.5  +       3    3896.871       1       2       0     0.5     0.5    1.00
 0.5  +       4     5729.26       1       3       0     0.5     0.5    1.00
 0.5  +       5    7480.338       1       4       0     0.5     0.5    1.00
 0.5  +       6    9145.132       1       5       0     0.5     0.5    0.00
 0.5  +       7   10716.163       1       6       0     0.5     0.5    0.00
 0.5  +       8   12182.207       1       7       0     0.5     0.5    0.00
 0.5  +       9   13525.788       1       8       0     0.5     0.5    0.00
 0.5  +      10   14718.082       1       9       0     0.5     0.5    0.00
 0.5  +      11   15709.384       1      10       0     0.5     0.5    0.00
end

The ab initio potential energy curve can be kept to control the shape of the refined curve:

 abinitio poten 1
 units cm-1 angstroms
 name 'X2Sigma+'
 lambda 0
 symmetry +
 mult   2
 type grid
 values   
 0.60     105169.63
 0.65      77543.34
 0.70      55670.88
 0.75      38357.64
 0.80      24675.42
 0.85      13896.77
 0.90       5447.96
 0.95      -1125.87
 1.00      -6186.94
 1.05     -10024.96
 1.10     -12872.63
 1.15     -14917.62
 1.20     -16311.92
 1.25     -17179.13
 1.30     -17620.16
 1.32     -17696.29
 1.33     -17715.26
 1.34     -17722.22
 1.35     -17717.69
 1.36     -17702.19
 1.37     -17676.19
 1.38     -17640.16
 1.40     -17539.76
 1.45     -17142.53
 1.50     -16572.59
 1.55     -15868.72
 1.60     -15063.34
 1.65     -14183.71
 1.70     -13252.86
 1.80       -11313.
 1.90      -9369.74
 2.00      -7518.32
 2.10      -5832.29
 2.20      -4366.71
 2.30      -3155.94
 2.40      -2208.98
 2.50      -1507.72
 2.60      -1013.23
 2.80       -456.87
 3.00       -221.85
 3.50        -72.13
 4.00        -41.65
 4.50         -24.9
 5.00        -14.32
 6.00         -4.74
 8.00         -0.75
 10.00        -0.19
 20.00          0.0
end

Intensities

For intensity calculations one needs an electric dipole moment curve (taken from http:https://exomol.com/db/BeH/9Be-1H/Yadin/9Be-1H__Yadin__LEVEL8.0.inp) and an Intensity section (BeH_Koput_04.inp):

dipole  1 1
name "<2Sigma+|DMZ|2Sigma+>"
spin   0.5 0.5
lambda  0  0
type   grid
values 
   0.400     -0.4166624920
   0.500     -0.0241871531
   0.600      0.2217732500
   0.700      0.3386323420
   0.800      0.3661076190
   0.900      0.3311512400
   1.000      0.2513061130
   1.100      0.1379591390
   1.200     -0.0012406430
   1.300     -0.1588361650
   1.320     -0.1920270000
   1.340     -0.2256736540
   1.350     -0.2426539090
   1.360     -0.2597311920
   1.400     -0.3288944440
   1.500     -0.5056369720
   1.600     -0.6824442480
   1.700     -0.8513506410
   1.800     -1.0025214800
   1.900     -1.1238133700
   1.950     -1.1687609400
   2.000     -1.2005094800
   2.020     -1.2089972000
   2.050     -1.2166847200
   2.070     -1.2181089800
   2.100     -1.2136337000
   2.300     -1.0182994100
   2.400     -0.8538885220
   2.500     -0.6736179730
   2.600     -0.5046631750
   2.700     -0.3634556350
   2.800     -0.2548814520
   2.900     -0.1758884440
   3.000     -0.1201861300
   3.100     -0.0815224742
   3.200     -0.0549121655
   3.300     -0.0367099205
   3.400     -0.0243335573
   3.500     -0.0159701097
   3.600     -0.0103484461
   3.700     -0.0065800412
   3.800     -0.0040495078
   3.900     -0.0023383813
   4.000     -0.0011684378
   4.200      0.0002034367
   4.400      0.0008546009
   4.600      0.0011177434
   4.800      0.0011645509
   5.000      0.0011023829
   6.000      0.0005429083
   8.000     -0.0000033249
  10.000     -0.0000085504
end
    
INTENSITY
 absorption
 thresh_intes  1e-30
 thresh_line   1e-30
 temperature   300.0
 nspin         1.5  0.5 (see Wikipedia isotope Be)
 linelist   BeH
 J,  0.5, 10.5
 freq-window   0.0,  7000.0
 energy low   -0.001, 5000.00, upper   -0.00, 12000.0
END

This will produce a line list for BeH in ExoMol format in two files .states and .trans, which can be processed using ExoCross, see ExoCross tutorial

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