Determination of geometrical, spectroscopic, thermal and nonlinear optical parameters of (+)-Varitriol by DFT/ab initio calculations V. Vasantha Kumar a , M. Nagabhushanam a,⇑ , J. Laxmikanth Rao b,⇑ a Department of Physics, University College of Science, Osmania University, Hyderabad 500 007, Andhra Pradesh, India b I&PC Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, Andhra Pradesh, India highlights  Computational studies on (+)- Varitriol have been carried out using ab initio and DFT methods.  Vibrational frequencies obtained from B3LYP method are in good agreement with the experiment.  The complete assignments are performed on the basis of the potential energy distribution (PED).  Thermodynamic and nonlinear optical properties have been calculated and reported.  Effect of temperature on various thermodynamic properties have been calculated and reported. graphical abstract article info Article history: Received 15 February 2013 Received in revised form 10 June 2013 Accepted 17 June 2013 Available online 11 July 2013 Keywords: (+)-Varitriol FT-IR spectra Micro-Raman spectra DFT calculations Hyperpolarizability Thermodynamic properties abstract Theoretical studies have been carried out on (+)-Varitriol using both the B3LYP/6-311+G and HF/6-311+G methods. The vibrational spectra of the title molecule have been recorded in solid state with FT-IR and Micro-Raman spectrometry. The calculated geometrical parameters of the title molecule, like bond length, bond angle and dihedral angles have been compared with the experimental data. The spectral fre- quencies have been calculated theoretically using both the above mentioned methods and are compared with the observed spectra. The complete vibrational assignments of wavenumbers have been made on the basis of potential energy distribution (PED). From this analysis, it is seen that the vibrational frequen- cies obtained from B3LYP method are in good agreement with the experiment, when compared to HF method. Nonlinear optical properties like dipole moment, hyperpolarizabilities and thermal properties like rotational constants, zero point vibrational energies are calculated. The effect of temperature on var- ious thermodynamic properties have been calculated and reported. Ó 2013 Elsevier B.V. All rights reserved. Introduction Fungi isolated from the marine environment plays an important role in large number of biological properties. During their lifespan, fungi metabolize and produce a broad range of organic compounds, from simple to very complex in nature. Among them, (+)-Varitriol (1) a tetrahydrofuran derivative, isolated from the marine derive strain of the fungus Emericella variecolor and is a potent cytotoxic in nature [1]. Barrero et al reported the isolation and structure elu- cidation of (+)-Varitriol [2]. The cytotoxic activity showed by 1 is more than 100-fold increased in potency towards the renal, breast and CNS cancer where it is lower in potency against leukemia, prostate, ovarian and colon cancer cell lines [2]. Due to its fascinat- ing biological activity towards cancer, it is very interesting to study the geometrical, vibrational, thermal and nonlinear optical proper- ties of the title molecule. Density functional theory (DFT) is becom- ing more useful to experimentalists in computing the geometrical 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.06.051 ⇑ Corresponding authors. E-mail address: lkjoshiji@yahoo.com (J. Laxmikanth Rao). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 116 (2013) 31–40 Contents lists available at SciVerse ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa