in this paper,the molecular geometry for three tautomers of uracil and four tautomers of cytosine has been analyzed. vibrational ir spectra of the tautomers were   investigated at hf and b3lyp level using the ab initio 6-31g* and lanl2dz basis sets from the program package gaussian 98 (a.7 public domain version). the physico-chemical and biochemical properties of uracil and cytosine are one of...

ab initio calculations were employed to investigate nitrogen inversion as a configuration change that can supply an infinitely useful switchable control mechanism for some complex systems. in this paper, design of a new artificial molecular nanohinge is discussed based on nitrogen inversion in which reciprocating motion of substituent in effect of inversion phenomenon, led to an open–close moti...

to get a mole of a gas, it is necessary to calculate the intermolecular interaction. theseintermolecular interactions can be depicted by drawing the potential energy of a pair molecule inrelation to the distance. the intermolecular potential energy surface in the mixtures of ch4-h2cogases from ab initio calculations has been explored. in ab initio calculations the basis setsuperposition error (...

an ab initio and density functional theory (dft) study about conformational analysis of tripeptide model hco−gly−l−ile−gly−nh2 is presented. the tripeptide was scanned about initial, central, and final residues, separately while for every scanning procedure the two other residues had been kept in the β conformation and side chain (sc) dihedral angles were maintained on the gauche− (g‾) state (χ...

ab initio calculations at hf/6-31g* level of theory for geometry optimization and mp2/6-31g*//hf/6-31g*for total energy calculation are reported for z-cyclooctene (1). the most favorable conformation of 1 is theunsymmetric boat-chair (1-bc) geometry. potential energy profiles for two different boat-chair/boat-chairinterconversion processes were calculated. the process via a chair transition sta...

To get a mole of a gas, it is necessary to calculate the intermolecular interaction. Theseintermolecular interactions can be depicted by drawing the potential energy of a pair molecule inrelation to the distance. The intermolecular potential energy surface in the mixtures of CH4-H2COgases from ab initio calculations has been explored. In ab initio calculations the basis setsuperposition error (...

ab initio calculations at hf/6-31g* level of theory for geometry optimization and mp2/6-31g*//hf/6-31g* for a single point total energy calculation are reported for the importantenergy-minimum conformations and transition-state geometries of 1, 3-diazacyclohepta-1, 2-diene (2) and 1, 3-diazacycloocta-1, 2-diene (3). the c2 symmetric twist-chair (2-tc)conformation of 2 is calculated to be 7.4 kj...

for better understanding of conformational stability of the dipeptide model hco—gly—l—leu—nh2,ab initio and dft computations at hf/6-31g(4 6-311++g(d,p) and b3lyp/6-31g(d) levels oftheory were carried out. geometry optimization of the dipeptide within the leucine (leu) side chainangles (x2 ,x2) resulted in three stable conformations as followings: anti-anti, the most stable one,(xi = 180°, x2 =...

bcn compounds have been researched theoretically and experimentally widely. in this paper, weintroduce the theoretical prediction of ternary b-c-n compounds. nmr spectroscopy was employedextensively to study these ternary nanostructures. we discuss the utilization of chemical shiftinformation as well as ab initio calculations of nuclear shielding for h20134c9n4 structuredetermination. we calcul...