On the importance of configurational sampling in theoretical calculation of electronic properties of complex molecular systems: Acetone in water

1000. D’Abramo^a, M. Aschi^{b, 1}, A. Di Nola^a and Andrea Amadei<sup>c,
      
      a</sup>Dipartimento di Chimica, Università di Roma, ‘La Sapienza’ P.le Aldo Moro 5, 00185 Roma, Italy
      ^bDipartimento di Chimica, Ingegneria Chimica e Materiali, Università de l’Aquila, via Vetoio (Coppito 1), 67010 l’Aquila, Italy
      ^cDipartimento di Scienze e Tecnologie Chimiche, Università di Roma ‘Tor Vergata’, Via della Ricerca, Scientifica, 1, I-00133 Roma, Italy
      
      Received 7 April 2006;  revised 18 April 2006.  Available online 27 April 2006.

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Abstract

In this work, we address the problem of the role and relevance of the aqueous environment configurational sampling on acetone electronic properties: the (vertical) absorption spectrum and corresponding excitation Helmholtz free energy. By comparing the results obtained by applying the perturbed matrix method (PMM) on molecular dynamics (MD) trajectories of different sampling efficiency, we specifically quantify the effects of the phase space sampling on acetone vertical electronic excitations. Results confirm that PMM provides an accurate and physically consistent description of the electronic excitation processes and show the crucial importance of an extended configurational sampling of the solvent environment in order to obtain a reliable (chromophore) absorption behaviour.