In the first step, we will check the installation and run BEx1D tools, anyway.

Preparation

1. Build BEx1D from source files or unpack the pre-built binaries (available for Windows only) according to the instructions described in the Installation section.
2. Ensure that the BEx1D executables reside in the directory where PATH is set.   The setpath.bat, setpath.csh, and setpath.sh in the sample folder may be usefull for this purpose.
3. Ensure that sample input files are in the current directory.

Sample input files brief

  The file named 'wagOHbenTSabs.fit' is a sample input file for anharmonic wagging vibration of OH in the TS (transition state) of hydrogen abstraction reaction from benzene by OH radical.   The second sample, 'nprCH2.fit', is a typical low-barrier hindered rotation of CH₂ in n-propyl radical.   The third, 'c2h2TSbendHH.fit', is two-dimensional internal rotation of the TS of C₂(X) + H₂ reaction.

Running bx1VIBsol (with wagOHbenTSabs.fit)

1. Run bx1fitPlls as:
   bx1fitPlls wagOHbenTSabs
2. The bx1fitPlls program derives a potential function from the input, and it should report the results of regression analysis as:

   ===== results of linear least squares regression =====
   Function:
    y = a0 + a1 * x^2 + a2 * x^4 + a3 * x^6 + a4 * x^8 + a5 * x^10 + a6 * x^12
   Optimum parameters (+-) standard deviations (relative)
    a0 = -1.0306367e+000 (+-)  1.3167189e+000 ( 127.76 %)
    a1 =  1.2877844e+003 (+-)  2.0212666e+001 (   1.57 %)
    ...

3. Re-check the installation and preparation if it did not work properly.
4. You will also find a new file, 'wagOHbenTSabs.inp', which is an input for bx1VIBsol.   Then, run bx1VIBsol as:
   bx1VIBsol wagOHbenTSabs
5. The bx1VIBsol solves the eigen problem of a Schrödinger equation, and will print diagnostic message as:

   estimated eigenvalue error is 1% at quntum number = 220.
   estimated partition function error is 6.2394e-046 at 2000 K.

6. Two files, 'wagOHbenTSabs_eigen_values.csv' and 'wagOHbenTSabs_part_funcs.csv', will be created.   These files contain the essential outputs, eigenvalues and partition function.

Running bx1HRsol (with nprCH2.fit)

1. Run bx1fitPlls as:
   bx1fitPlls nprCH2
2. The output would look like:

   ===== results of linear least squares regression =====
   Function:
    y = a0 + a1 * cos(2*x) + a2 * cos(4*x) + a3 * cos(6*x) + a4 * cos(8*x) + a5 * cos(10*x) + a6 * cos(12*x) + a7 * cos(14*x) + a8 * cos(16*x) + a9 * cos(18*x)
    y' = a1 * -2*sin(2*x) + a2 * -4*sin(4*x) + a3 * -6*sin(6*x) + a4 * -8*sin(8*x) + a5 * -10*sin(10*x) + a6 * -12*sin(12*x) + a7 * -14*sin(14*x) + a8 * -16*sin(16*x) + a9 * -18*sin(18*x)
    y" = a1 * -4*cos(2*x) + a2 * -16*cos(4*x) + a3 * -36*cos(6*x) + a4 * -64*cos(8*x) + a5 * -100*cos(10*x) + a6 * -144*cos(12*x) + a7 * -196*cos(14*x) + a8 * -256*cos(16*x) + a9 * -324*cos(18*x)
   Optimum parameters (+-) standard deviations (relative)
    a0 =  3.7021012e+001 (+-)  0.0000000e+000 (   0.00 %)
    a1 =  3.1151841e+001 (+-)  0.0000000e+000 (   0.00 %)
    ...

3. Run bx1HRsol with a new file, 'nprCH2.inp', as:
   bx1HRsol nprCH2
4. Find four new files created, namely, 'nprCH2_eigen_funcs00.csv', 'nprCH2_eigen_values.csv', 'nprCH2_eigen_vectors00.csv', and 'nprCH2_part_funcs.csv'.   These are outputs of; eigenfunctions, eigenvalues, eigenvectors, and partition function, respectively.

Running bx1S2HRsol (with c2h2TSbendHH.fit)

1. Run bx1fitPlls as:
   bx1fitPlls c2h2TSbendHH
2. The output would look like:

    ===== results of linear least squares regression =====
    Function:
     y = a0 + a1 * x^2 + a2 * x^4 + a3 * x^6 + a4 * x^8 + a5 * x^10 + a6 * x^12
    Optimum parameters (+-) standard deviations (relative)
     a0 =  8.2167758e+002 (+-)  1.0620381e-001 (   0.01 %)
     a1 = -1.0533809e+003 (+-)  4.2637489e+000 (   0.40 %)
    ...

3. Run bx1S2HRsol with a new file, 'c2h2TSbendHH.inp', as:
   bx1S2HRsol c2h2TSbendHH
4. Find four new files created, namely, 'c2h2TSbendHH_eigen_values.csv', 'c2h2TSbendHH_part_funcs.csv'.   These are outputs of; eigenvalues and partition function, respectively.