ORIGINAL PAPER Rovibrational energy and spectroscopic constant calculations of CH 4 ⋯ CH 4 , CH 4 ⋯ H 2 O, CH 4 ⋯ CHF 3 , and H 2 O ⋯ CHF 3 dimers Wiliam F. Cunha & Ricardo Gargano & Edgardo Garcia & José R. S. Politi & Alessandra F. Albernaz & João B. L. Martins Received: 3 February 2014 /Accepted: 5 May 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract In this work, we performed a thorough investigation of potential energy curves, rovibrational spectra, and spectro- scopic constants for dimers whose interactions are mediated by hydrogen bonds and other hydrogen interactions. Particularly, we deal with CH 4 ⋯CH 4 , CH 4 ⋯H 2 O, CH 4 ⋯CHF 3 , and H 2 O⋯CHF 3 dimers by employing accurate electronic energy calculations with two different basis sets at the MP2 level of theory. Following this, the discrete variable representation method was applied to solve the nuclear Schrödinger equation, thus obtaining spectroscopic constants and rovibrational spec- tra. The harmonic constant, ω e , presents a direct relation to the strength of dimer interactions. As a general rule, it was found that a decrease of interatomic distances is followed by the increase of D e for all dimers. This behavior suggests that the interaction of CH 4 ⋯CH 4 is the weakest among all dimers, followed by CH 4 ⋯CHF 3 , CH 4 ⋯H 2 O and the strongest interaction given by the H 2 O⋯CHF 3 dimer. Keywords Dimers . Rovibrational spectra . Potential energy curve . MP2 Introduction Noncovalent interactions are key factors to understanding many fundamental properties of chemical systems and processes. Despite being of much smaller magnitude when compared to covalent interactions, non-covalent phenomena are essential, for example, for the stability of biomolecules such as proteins [1] and nucleic acids [2] as well as for the physical-chemistry understanding of different environmental- ly important compounds [3, 4]. On the other hand, the de- scription of this kind of interaction is known to require a great deal of resources, demanding sophisticated computational methods from both the level of theory applied and the basis set used [5]. A frequent procedure to overcome this difficulty is to use dimer calculations as a starting point in considering complex systems [6]. Additionally, determining intermolecu- lar interactions experimentally show difficulties that reside at limited sampling and thermodynamic conditions to yield a potential energy surface [7]. Alternatively, intermolecular po- tentials are easily obtained through theoretical methods. Fur- thermore, the theoretical study of dimers consists of a standard technique in quantum chemistry and the properties that tend to alter their behavior are of fundamental importance in under- standing many systems of technological interest. Many researchers have investigated structural features of molecular clusters [8]. By studying the behavior of dimers, one can infer properties of larger clusters in an elegant and accurate fashion due to the possibility of applying computation of the highest level in small systems. Among these properties, the rovibrational spectra deserve special attention since a com- parison between experimental and theoretical data consists on an unequivocal way to determine whether the performed cal- culation is suitable for each particular system [9, 10]. It is well known that the Coulombic term contribution plays a central role in the interaction energy of dimers, regardless the species considered. Thereupon, the behavior of dimers on which different kinds of multipole expansion moments primarily act has been extensively investigated in the last years [3, 4]. Of particular interest are those dimers originating from hydrogen bonding or another kind of hydrogen-mediated This paper belongs to Topical Collection Brazilian Symposium of Theoretical Chemistry (SBQT2013) W. F. Cunha : R. Gargano : A. F. Albernaz Institute of Physics, University of Brasilia, Brasilia 70919-970, Brazil E. Garcia : J. R. S. Politi : J. B. L. Martins (*) Institute of Chemistry, University of Brasilia, Brasilia 70919-904, Brazil e-mail: lopes@unb.br J Mol Model (2014) 20:2298 DOI 10.1007/s00894-014-2298-1