ORIGINAL PAPER First principles investigations of vinazene molecule and molecular crystal: a prospective candidate for organic photovoltaic applications Mazmira Mohamad & Rashid Ahmed & Amirudin Shaari & Souraya Goumri-Said Received: 21 November 2014 /Accepted: 12 January 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract Escalating demand for sustainable energy resources, because of the rapid exhaustion of conventional energy resources as well as to maintain the environmental level of carbon dioxide (CO 2 ) to avoid its adverse effect on the climate, has led to the exploitation of photovoltaic technology manifold more than ever. In this regard organic materials have attracted great attention on account of demonstrating their potential to harvest solar energy at an affordable rate for photovoltaic technology. 2-vinyl-4,5- dicyanoimidazole (vinazene) is considered as a suitable material over the fullerenes for photovoltaic applications because of its particular chemical and physical nature. In the present study, DFT approaches are employed to provide an exposition of opto- electronic properties of vinazene molecule and molecular crystal. To gain insight into its properties, different forms of exchange correlation energy functional/potential such as LDA, GGA, BLYP, and BL3YP are used. Calculated electronic structure of vinazene molecule has been displayed via HOMO-LUMO isosurfaces, whereas electronic structure of the vinazene mo- lecular crystal, via electronic band structure, is presented. The calculated electronic and optical properties were analyzed and compared as well. Our results endorse vinazene as a suitable material for organic photovoltaic applications. Keywords DFT . HOMO-LUMO . Optical spectra . Organic photovoltaic . Vinazene Introduction Repaid demand for sustainable energy resources has increased more than ever because of threatening catastrophic changes in global climate by emission of greenhouse gases from conven- tional energy resources via combustion process. In addition, conventional resources of energy have speedily fallen. There- fore extensive efforts are being done to search for such alter- nate energy systems which can fulfill future energy require- ments alongside stabilizing the atmospheric CO 2 level to pre- serve a friendly environment [1, 2]. In this regard photovoltaic systems are considered to be perfect candidates. Photovoltaic is the technology that harvests the solar energy by converting the solar radiations directly into electricity. Because of having huge potential of supplying approximately 10 4 times larger energy than our present needs, solar energy is expected to be the best solution for the problem [3, 4]. Global industrial sectors have progressed significantly in exploitation of photovoltaic technologies that relied largely upon inorganic materials like silicon over a decade ago. Though inorganic materials have shown their performance well in photovoltaic devices, several disadvantages in terms of high cost and limited resources have sparked the interest among researchers to explore and investigate the replacement of inorganic materials. Beside inorganic materials, from the beginning of the twenty first century, organic materials have also shown ample potential for photovoltaic (PV) systems [5–7]. Therefore, in the present era, considerable attention is being focused on organic materials in order to search for M. Mohamad : R. Ahmed : A. Shaari Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM, Skudai 81310, Johor, Malaysia R. Ahmed e-mail: rashidahmed@utm.my R. Ahmed e-mail: Souraya.Goumri-Said@chemistry.gatech.edu S. Goumri-Said (*) School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA e-mail: sgs8@gatech.edu J Mol Model (2015) 21:27 DOI 10.1007/s00894-015-2582-8