排序方式: 共有78条查询结果,搜索用时 15 毫秒
11.
Somayeh KhazaeiMohammad Khazaei Hosein CheraghchiVahid Daadmehr Yoshiyuki Kawazoe 《Physica B: Condensed Matter》2011,406(20):3885-3890
We have used a non-equilibrium surface Green's function matching formalism combined with a tight-binding Hamiltonian to consider the effect of different arrangements of pentagon rings on localization of density of states at the tip regions of semi-infinite capped carbon nanotubes. The transfer matrixes are obtained by an iterative procedure. The results demonstrate that the positions of the peaks near Fermi energy are remarkably affected by the relative locations of pentagons. It is observed that in thin nanotubes, carbon atoms belonging two neighboring pentagon rings have significant contribution in the localized states near fermi energy. From our calculations, it turns out that the metallic or semiconducting behavior of capped nanotubes in the tip regions depends on the metallic or semiconducting nature of their nanotube stems. 相似文献
12.
Khazaei M Liang Y Bahramy MS Pichierri F Esfarjani K Kawazoe Y 《J Phys Condens Matter》2011,23(40):405403
We have performed a set of first-principles simulations to consider the possible phase transitions in molecular crystals of HCN under high pressure. Our calculations reveal several transition paths from the orthorhombic phase to tetragonal and then to triclinic phases. The transitions from the orthorhombic to the tetragonal phases are of the second order, whereas those from the tetragonal to the triclinic phases turn out to be of the first-order type and characterized by an abrupt decrease in volume. Our calculations show that, by adjustment of the temperature and pressure of the HCN molecular crystal, novel layered and polymeric crystals with insulating, semiconducting or metallic properties can be found. Based on our simulation results, two different crystal formation mechanisms are deduced. The stabilities of the predicted structures at ambient pressure are further assessed by performing phonon or MD simulations. In addition, the electron transport properties of the predicted polymers are obtained using the non-equilibrium Green's function technique combined with density functional theory. The results show that the polymers have metallic-like I-V characteristics. 相似文献
13.
Reaction of substituted benzene rings with N‐bromophthalimide, under neutral conditions, gave the corresponding bromo derivatives with a preference for the formation of the para bromo isomer over the ortho isomer. The simple work‐up procedure minimizes loss of product and the yields are good. 相似文献
14.
M. A. Zolfigol A. Khazaei E. Kolvari N. Koukabi M. Gilandoust 《Journal of the Iranian Chemical Society》2011,8(4):1058-1062
The use of chlorine bleach (5% NaOCl) for the halogenation-oxidation of oximes to gem-chloronitro compounds is reported. Chlorine bleach afforded satisfactory yields when employed alone either at room temperature or under ultrasonic irradiation. 相似文献
15.
M. Khazaei A. Malekzadeh F. Amini Y. Mortazavi A. Khodadadi 《Crystal Research and Technology》2010,45(10):1064-1068
In this study the effects of citric acid concentration, used as organic emulsifier, on the perovskite phase formation of the nano strontium manganite or cobaltite samples were studied. Stoichiometric perovskites in the absence and presence of citric acid were prepared by drying a solution containing molar ratio of Sr(NO3)2/Mn(NO3)2·4H2O and Sr(NO3)2/Co(NO3)2·6H2O = 1 followed by calcination at 900 °C for 5 h. Citric acid concentration, selected to be 0.0, 0.3, 0.6, 1.0, 1.3, 2.5 and 5 times of the total number of moles of the nitrate ions. The results revealed that increase in the citric acid concentration, larger than number of moles of the nitrate ions equivalent, deteriorates the perovskite phase formation. Instead, a new phase of carbonates and metal oxides are appeared. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
Fathtabar Abbas Khazaei Ali Akbar Ghezelbigloo Asadallah 《Wireless Personal Communications》2021,117(2):577-589
Wireless Personal Communications - A new Direction of arrival (DOA) estimation method for wideband coherent sources is presented in this paper. This method does not require any prior knowledge of... 相似文献
17.
Lee SU Khazaei M Pichierri F Kawazoe Y 《Physical chemistry chemical physics : PCCP》2008,10(34):5225-5231
We present a systematic analysis of electron transport characteristics of carbon nanotube (CNT) intramolecular heterojunctions with peptide linkages, MM, SS, SM1, and SM2 where M and S stand for metallic and semiconducting CNT electrodes, respectively. Our theoretical investigations show that the incorporation of peptide linkages and their associated dipole moments play an important role in determining the electron transport characteristics and lead to materials with unique properties, such as Schottky-like behavior. Furthermore, we show that the Schottky-like behavior is observed in our SM1 junction but not in the SM2 junction because of the different effects that arise from both the direction and strength of their dipole moments. We believe that our results will pave the way towards the design and implementation of various electronic logic functions based on carbon nanotubes for applications in the field of nanoelectronics. 相似文献
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19.
Ardeshir Khazaei Mohammad Ali Zolfigol Mohmmad Mokhlesi Fateme Derakhshan Panah Sami Sajjadifar 《Helvetica chimica acta》2012,95(1):106-114
Two simple, mild, and efficient procedures for the thiocyanation of N‐heterocycles, substituted anilines (electron‐rich and electron‐deficient), and N‐substituted aromatic amines at room temperature are reported (Table 3). The first uses H2O2 as pollution‐free oxidant and the second H5IO6; both with the reagent potassium thiocyanate in H2O as solvent. These procedures provided the target thiocyanates after a short reaction time in good to excellent yields and high regioselectivity. 相似文献
20.
Akbarpoor Tahere Khazaei Ardeshir Seyf Jaber Yousefi Sarmasti Negin Gilan Maryam Mahmoudiani 《Research on Chemical Intermediates》2020,46(2):1539-1554
Research on Chemical Intermediates - In the present research, the eggshell as a hazardous waste by European Union regulations was converted to a valuable catalyst, namely nano-Fe3O4@(HSO4)2. The... 相似文献