ORIGINAL PROGRAMS

M.L. Senent

 

ENEDIM

FIT-ESPEC

 

 

ENEDIM (2001) is a variational Fortan code developed for the determination of band positions, intensities and molecular spectroscopic parameters NON-RIGID MOLECULES. Initial data are Potential Energy Surfaces depending on 1, 2, 3, 4 or low and medium frequency modes.

SCHEME

(see previous results in Ref.[1.1-1.7]

 

References

 

[1.1] An ab initio structural and spectroscopic study of acetone. An analysis of the far infrared torsional spectra of acetone ‑h6 and ‑d6, Y.G. Smeyers, M.L. Senent, V. Botella and D.C. Moule, J.Chem.Phys, 98 (4), 2754-2767 (1993).

[1.2] An ab initio determination of the bending-torsion-torsion spectrum of dimethyl‑ether, (CH3)2O and (CD3)2O, M.L. Senent, D.C. Moule and Y.G. Smeyers, J.Chem.Phys., 102 (15), 5952-5959 (1995)

[1.3] Ab initio calculations and analysis of the torsional spectra of dimethyl‑amine and dimethyl‑phosphine, M.L.Senent and Y.G.Smeyers, J.Chem.Phys., 105 (7), 2789-2797 (1996)

[1.4] Ab initio determination of the far infrared spectra of some isotopic varieties of ethanol, M.L.Senent, Y.G.Smeyers, R.Dominguez-Gómez and M.Villa, J.Chem.Phys. 112 (13), 5809-5819 (2000).

[1.5] Ab initio determination of the torsional spectra of acetic acid, M.L.Senent, Mol.Phys, 99 (15), 1311-1321 (2001).

[1.6] Ab initio determination of the torsional spectrum of glycolaldehyde, M.L.Senent, J.Phys.Chem.A. 108(30), 6286-6293 (2004)

[1.7]Ab initio study of the rotational-torsional spectrum of methyl format, M.L.Senent, M.Villa, F.J.Meléndez y R. Domínguez-Gómez, ApJ, 627, 567-576 (2005).

[1.8] Dermination of the kinetic energy parameters of non-rigid molecules, M.L.Senent, Chem.Phys.lett., 296, 299-306 (1998)

[1.9] Ab initio determination of the roto-torsional energy levels of trans-1,3-butadiene, M.L.Senent, J.Mol.Spectrosc., 191, 265-275 (1998)

[1.10]The Möller-Plesset perturbation theory applied to the determination of non-rigid molecule vibrational levels, M.L.Senent and R.Domínguez-Gómez, Chem.Phys.Lett., 351 (3/4), 251-258 (2002)
 

 

 

 

FIT-ESPEC (2007) is a fortran code developed for the determination of molecular spectroscopic parameters with Perturbation Theory. The input data are the total electronic energies of a Grid of geometries defined close to the local minima.

SCHEME

(see previous results in Ref. [2.1-2.2])

FIT-ESPEC is a package of Fortran 77 subroutines designed for the determination of spectroscopic properties of semi-rigid molecules using Second Order Perturbation Theory. The starting point is an ab initio anharmonic force field.

      The present version (FIT-ESPEC 2007) allows us the study of molecular species containing non-degenerate and bi-degenerate vibrational modes without any restriction concerning the type or size of the molecular system. It is adequate for the treatment of asymmetric and symmetric tops and linear molecules.

      The subroutines are classified in two sections: FIT and ESPEC. FIT allows us the linear fitting of an analytical 3N-6 dimensional Potential Energy Surface, the minimization and later determination of the corresponding quadratic, cubic and cuartic derivatives. ESPEC transforms the derivatives expressed in curvilinear internal coordinates to dimensionless normal coordinates following the methodologies of Hoy et al [2.3]. The actual version allows us the determination of harmonic and anharmonic fundamentals, band positions, vibrational spectroscopic parameters, and the parameters of reduced Watson Hamiltonian [2.4]. Future version that are in preparation, will allow us to determine ro-vibrational levels and intensities.

FIT  By default FIT performs least square linear fits to analytic 3N-6 functions. Initial data are the total electronic energies and coordinates of a GRID of NP geometries selected close to the local minima. By default, products of Polynomials series, Fourier series and Morse Oscillator are employed, in spite of the program can integrate of any functions. It performs non linear fits and allows us the treatment of global surfaces.

           FIT contains the following subroutines:

 a) ISO-X subroutines, for the transformations of coordinates. They transform cartesian to curvilinear internal or symmetry adapted internal coordinates, and vice versa, and classified the points in one, two, multi-excitations with respect a structure of reference.

b) PEARSON-X subroutines, for the selection of the more effective basis functions for the fitting searching for shortest series. Automatically, the functions which are equal to zero or insignificant for all the geometries are eliminated. Pearson product-moment correlation coefficients and covariance matrix are determined.

c) Subroutines for linear and non linear fit.

d) DATA-X are a set of subroutines for the "cleaning" of the Potential Energy Surface. They perform and statistical study of the initial data to search erroneous values. The possibility of human errors performing the ab initio calculations or classifying the results has to be taken into consideration especially for very large molecules. Also, in species of low stability or multi-configurational systems, numerical errors may be expected. These "erroneous" or "suspicious" data are eliminated following statistical criteria based on the determination of the R2 parameter.

For this purpose, the matrix CRITERIA(i,j) elements are calculated (i = one of the NP geometries and j= 1, ...,5), following the schema:

Two potential energy surfaces are employed. The full analytical function:

and a reduced surface:

An average energy is defined for the Total Electronic Energies deriving from the ab initio calculations:

If EiV, and EiVr are the corresponding values obtained from the fitting to V and Vr, and Eij are the corresponding values obtained from a fit to V after the elimination of the j geometry, we can defined:

 

where:

         

and R2 is the Multiple Correlation Coefficient defined considering the whole of the data.

 f) DERIV- X subroutines for the determination the potential energy surface derivatives calculated at the local minimum. Several subroutines write the PES, force field, minimum energy geometry for ESPEC. Intermediate results are writing for an easy control of the program.

 

References

 

[2.1] Anharmonic spectroscopic study of the ground electronic state of various C4 radical isotopomers, M.L.Senent H. Massó y M.Hochlaf, ApJ, 670, 1510 (2007)

[2.2] Ab initio characterization of the C5, H. Massó, V. Veryazov, P.-Å. Malmqvist, B.O. Roos y M.L.Senent, J.Chem.Phys., 127 (15), 154318 (2007)

[2.3] Anharmonic force constant calculations, A.R.Hoy, I.M.Mills and G.Strey, Mol.Phys., 24, 1265 (1972)

[2.4] Aspects of Quartic and sextic centrifugal effects on rotational levels, J.K.G.Watson, in “Vibrational spectra and structure” (Ed. J. Durig), Vol.6 p.1, Elelvier, Amsterdam (1977).