Ž.V. Kneževic

Bio: Ž.V. Kneževic is an academic researcher. The author has contributed to research in topics: Selenourea & Thiourea. The author has an hindex of 1, co-authored 1 publications receiving 67 citations.

Vibrational Analysis of Urea

Abstract: Although a lot of work has been done on the vibrational analysis of urea, there still remain some contradictions and uncertainties, mainly due to interpretation of the vibrational spectrum of crystalline urea based on force field calculations on isolated urea instead of on urea in its crystal phase. We have shown that this approach is not allowed in the case of urea. The vibrational spectrum of urea was interpreted by measuring the solid state infrared spectra of eight isotopomers of urea at room temperature and at −196 °C, and Raman spectra at room temperature and at −120 °C, and of a urea−water solution. Force field calculations from our recently published article on isolated urea and on urea in its crystal structure, at the Hartree−Fock level with a 6-31++G** basis set, were also used. We have also shown that high-pressure measurements using a “diamond anvil cell” are not useful by performing a vibrational analysis.

Sol−Gel Derived Urea Cross-Linked Organically Modified Silicates. 1. Room Temperature Mid-Infrared Spectra

Abstract: Organic−inorganic hybrids prepared by the sol−gel process are investigated by infrared spectroscopy at room temperature. The matrix of the so-called ureasils is a silica network to which oligopolyo...

Solids Modeled by Ab-Initio Crystal Field Methods. Part 17. Study of the Structure and Vibrational Spectrum of Urea in the Gas Phase and in Its P4̄21m Crystal Phase

Abstract: In this study the geometrical structure and vibrational spectrum are studied for the urea molecule (CO(NH2)2) in the gas phase as well as in its P421m crystal phase. Experimental frequencies for u...