排序方式: 共有45条查询结果,搜索用时 15 毫秒
31.
Carling K Wahnstrom G Mattsson TR Mattsson AE Sandberg N Grimvall G 《Physical review letters》2000,85(18):3862-3865
We have revealed, and resolved, an apparent inability of density functional theory, within the local density and generalized gradient approximations, to describe vacancies in Al accurately and consistently. The shortcoming is due to electron correlation effects near electronic edges and we show how to correct for them. We find that the divacancy in Al is energetically unstable and we show that anharmonic atomic vibrations explain the non-Arrhenius temperature dependence of the vacancy concentration. 相似文献
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Regioselective formation of the 7-azabicyclo[4,2,2]decanone (4) was accomplished by reaction of hydroxylamine with the enone (10) and subsequent reduction of the isoxazolidine adduct (11); intramolecular nitrone cycloaddition of (19) gave a 2:1 mixture of the regioisomers (17) and (18) which were reduced to give the bridgehead methylated,
-hydroxylated, [3,3,2] and [4,2,2] iminomethano compounds (5) and (6). 相似文献
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The synthesis and structural and magnetic characterization of 16 compounds AM(II)Fe(III)(C(2)O(4))(3) (A = N(n-C(3)H(7))(4), N(n-C(4)H(9))(4), N(n-C(5)H(11))(4), P(n-C(4)H(9))(4), P(C(6)H(5))(4), N(n-C(4)H(9))(3)(C(6)H(5)CH(2)), (C(6)H(5))(3)PNP(C(6)H(5))(3), As(C(6)H(5))(4); M(II) = Mn, Fe) are reported. X-ray powder diffraction profiles are indexed in R3c or its subgroup P6(5)22 or P6/mmm to derive unit cell constants. The structures of all the compounds consist of two-dimensional honeycomb networks [M(II)Fe(III)(C(2)O(4))(3)(-)](infinity). The M(II) = Fe compounds behave as ferrimagnets with T(c) between 33 and 48 K, but five exhibit a crossover from positive to negative magnetization near 30 K when cooled in a field of 10 mT. The compounds exhibiting this unusual magnetic behavior are those that have the highest T(c). Within the set N(n-C(n)()H(2)(n)()(+1))(4)Fe(II)Fe(III)(C(2)O(4))(3) (n = 3-5), T(c) increases with interlayer separation and the low-temperature magnetization changes from positive (n = 3) to negative (n = 4, 5). In the M = Mn(II) compounds, the in-plane cell parameter a(0) is approximately 0.03 ? greater than in the corresponding M = Fe(II) ones while the interlayer separation (c(0)/6) is on average 0.08 ? smaller. All members of the M(II) = Mn series have magnetic susceptibilities showing broad maxima at 55 K characteristic of two-dimensional antiferromagnetism, but the magnetization of several of the salts increases sharply below 27 K due to the onset of spin canting, the magnitude of which varies significantly with A. 相似文献
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Robert W. Carling 《Thermochimica Acta》1983,60(3):265-275
The heat capacities of NaNO3 and KNO3 were determined from 350 to 800 K by differential scanning calorimetry. Solid-solid transitions and melting were observed at 550 and 583 K for NaNO3 and 406 and 612 K for KNO3, respectively. The entropies associated with the solid-solid transitions were measured to be (8.43± 0.25) J K−1 mole−1 for NaNO3 and (13.8±0.4) J K−1 mole−1 for KNO3. At 298.15 K the values of C0P S0P, {H0(T)-H0(0)}/T and -{G0(T)-H0(0)}/T, respectively, are 91.94, 116.3, 57.73, and 58.55 J K−1 mole−1 for NaNO3 and 95.39, 133.0, 62.93, and 70.02 J K−1 mole−1 for KNO3. Values for S0T, {H0(T)-H0(0)}/T, and -{G0(T)-H0(0)}/T were calculated and tabulated from 15 to 800 K for NaNO3 and KNO3. 相似文献
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Carl-Johan Carling Mathieu L. Viger Viet Anh Nguyen Huu Arnold V. Garcia Adah Almutairi 《Chemical science》2015,6(1):335-341
Controlling chemistry in space and time has offered scientists and engineers powerful tools for research and technology. For example, on-demand photo-triggered activation of neurotransmitters has revolutionized neuroscience. Non-invasive control of the availability of bioactive molecules in living organisms will undoubtedly lead to major advances; however, this requires the development of photosystems that efficiently respond to regions of the electromagnetic spectrum that innocuously penetrate tissue. To this end, we have developed a polymer that photochemically degrades upon absorption of one photon of visible light and demonstrated its potential for medical applications. Particles formulated from this polymer release molecular cargo in vitro and in vivo upon irradiation with blue visible light through a photoexpansile swelling mechanism. 相似文献
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CJ Isham 《Contemporary Physics》2013,54(3):207-219
The paper contains a relatively non-technical summary of some recent work by the author and Jeremy Butterfield. The goal is to find a way of assigning meaningful truth values to propositions in quantum theory: something that is not possible in the normal, instrumentalist interpretation. The key mathematical tool is presheaf theory where multi-valued, contextual truth values arise naturally. We show how this can be applied to quantum theory, with the ‘contexts’ chosen to be Boolean subalgebras of the set of all projection operators. 相似文献