Table of contents

# Basic theses

## The goals of program development

1. Exploration of the possibilities of experimental methods for investigations of molecular structure.
2. Development of the gas electron diffraction (GED) method and automation of the all stages of GED investigation process.
3. Development of spectroscopic methods of molecular structure investigation.
4. Providing the ability to carry out "very accurate" researches due to extended facilities and flexibility of the program interface.
5. Elaboration of the joint methods of molecular structure investigations.

## Current possibilities

- Molecular structure research.

- Investigation of molecular structure by means of GED method.
- Investigation of molecular geometry using rotational constants.
- Investigation of molecular structure using GED data and rotation constants simultaneously.

- Gas electron diffraction.

- Static model of gas electron diffraction.
- Dynamic model of gas electron diffraction. Parametric form of potential function. Support for geometry, amplitudes and corrections relexation.
- Modelling of any mixtures of molecules with static and dynamic GED models. It is possible to model both mixtures of molecules with identical and different topology.
- Defining of molecular geometry as a z-matrix. The usage of internal geometrical parameters and cartesian coordinates as parameters is possible.
- Support for dummy atoms. With dummy atoms and the approach of z-matrices it is very simple to set any symmetry for a molecule.
- Automatic division of the mean square amplitudes into the groups.
- Smoothing of the model-dependent background by cubic splines or polynoms.
- Smoothing of the model-dependent background using sector function.
- Automatic calculation of the GED g-functions and atomic scattering.
- Unlimited number of points on the GED intensity curve. The non-equal steps on the intensity curve is allowable. Unlimited number of nozzle-to-plate distances. Unlimited number of intensity curves from each nozzle-to-plate distance.
- Initial processing of the GED experimental material.

- Work with image files. Support for uncompressed 8/16 bit files of TIFF format.
- Obtainig GED intensity curves from diffraction pattern images.
- Work with GED standards: estimation of the electron wavelengths and sector function. Support for benzene and CCl4 as a standards.
- Calibration of scanners. The possibility to calibrate "on the fly".
- Mrthods for the scanning quality control.

- Thermodynamics.

- Statistical thermodynamics. Model of ideal gas, rigid rotor-harmonic oscillator, uncoupled motions.

- Reverse problems.

- Powerful methods of minimization and functional minima finding criteria. It is possible to do a robust-minimization with iteratively reweighted experimental data.
- Variation of independent internal geometrical parameters, cartesian coordinates, dependent r_a distances, mean square amplitudes, GED scale factors, concentrations of molecules, parameters of a potential function. Variation by groups.
- Automatic calculation of the errors for dependent parameters.
- Searching of the global minimum by grid scanning of functional values, by Monte-Carlo method (randomization). The multidimensional scanning on any parameters is possible. The number of dimensions is unlimited, the number of points per parameter is unlimited. Scanning by groups.
- First-order local sensitivity analysis.

- Effectiveness.

- Flexible and convenient input format.
- Efficient usage of the SMP (multiprocessor/milticore) systems.
- Versions of program for OS/2 Warp, eComStation, FreeBSD, Linux, Windows.

## Conditions of program distribution.

The program is free. Conditions of it's distribution - "AS IS". The author does not guarantee the absense of errors, you use this program on your own risk. Transmission to other persons is prohibited.

## If you found error.

If you think that you have found error or some incorrectness in program and interested in correction of it, then you can write to me (Yura Vishnevskiy, y_v_vishnevsky@rambler.ru) an e-mail with indication on this error. Do not forget to tell me the program version number and to send input file on which UNEX gives incorrect results. In any case, I do not guarantee the fast correction of errors or modification/expanding of UNEX functionality.