CALCULATION OF ANHARMONICITIES IN OVERTONE MODES AND SMALL-CLUSTER SHIFTS OF SPHERICAL-TOP MOLECULES J. D. Fuhr, J. Fiol , E. Cortizo, P. Fainstein, D. Fregenal, T. Guozden, E. Kaúl, P. Knoblauch, A. Lamagna, P. Maceira, G. Rozas, M. Zarco Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Argentina Centro Atómico Bariloche (CNEA) 69 th ISMS - 2014 1 / 13
14
Embed
CALCULATION OF ANHARMONICITIES IN OVERTONE MODES …
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
CALCULATION OF ANHARMONICITIES INOVERTONE MODES AND SMALL-CLUSTERSHIFTS OF SPHERICAL-TOP MOLECULES
J. D. Fuhr, J. Fiol, E. Cortizo, P. Fainstein, D. Fregenal, T. Guozden,E. Kaúl, P. Knoblauch, A. Lamagna, P. Maceira, G. Rozas, M. Zarco
Centro Atómico Bariloche,Comisión Nacional de Energía Atómica, Argentina
Supersonic molecular beam jetswith mixed gases→ leads to Cluster formationNeed to investigate the Dynamics ofcluster formationExperimental analysis by IRabsorption spectroscopyShift of molecular lines(structure calculations)Determination of overtones inmolecules
Previous (a few) results on spherical-top molecules:“Monte-Carlo Simulation of Structural Properties and Infrared Spectra ofSF6-(Ar)n Clusters” D. Eichenauer and R. J. Le Roy J. Chem. Phys. 88, 2898(1988).“Two- vs. Three-Dimensional Melting and Spontaneous Reversing Isomerizationin Isolated SF6-(Ar)n Van der Waals Clusters” J. C. Shelly, R. J. Le Roy andF. G. Amar Chem. Phys. Lett. 152, 14 (1988).“Structure and IR-spectrum calculations for small SF6 clusters”; T. A. Beu andK. Takeuchi; J. Chem. Phys. 103, 6394 (1995).“Calculations of structure and IR-spectrum for small UF6 clusters ”; T. A. Beu,J. Onoe and K. Takeuchi; J. Chem. Phys. 106, 5910 (1997).
Perturbative calculations need inter-molecule interactionsUseful for (not so) small clusters
Ab-initio calculationsDetermination of inter-molecule interactionsDirect calculation of line shiftsComputationally expensive for very large clusters
Calculations using VSCF approximation.Grids of 16 points in each “direction”.About 30000 different energies calculated in approx. HF+MP2.Mode frequencies evaluated from the Hessian matrix.Degenerate modes must be treated differently.
We calculated harmonic and overtone modes of SF6 in HF-MP2approximationIncluded anharmonic effects in the framework of VSCF approximationObtained the non-spherical potential interactions for (SF6)(2,3) andSF6−(Ar)(1,2)
To Do:
Treatment of degenerate modes in VSCFCalculate fully 3D interactions for these and other similar systems