Lattice-Dynamic Calculation for Alkali Metals

Paul S. Ho

doi:10.1103/physrev.169.523

Strain-dependent structure and Raman behaviours in the heavy-ion irradiated manganite at extreme low dose

Scientific Reports ◽

10.1038/s41598-019-55638-1 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Nam Nhat Hoang ◽

Duc Huyen Yen Pham ◽

The Nghia Nguyen

Keyword(s):

Density Functional ◽

Structural Changes ◽

Low Dose ◽

Blue Shift ◽

Heavy Ion ◽

Dynamic Calculation ◽

Functional Theory ◽

Lattice Dynamic Calculation ◽

Strain Dependent ◽

Shed Light

AbstractThe microstrains in heavy-ion irradiated manganite LaMnO3 can be managed in linear response of irradiation dose, and the corresponding internal pressure up to 8 GPa can be induced by varying doses. The response of structure under stress is studied by means of Density Functional Theory and Lattice Dynamic Calculation. All obtained Raman scattering lines are discussed in details to shed light onto structural changes during ion implantation. There appears new resonance peak at around 550 cm−1, which splits from broad features in the spectra, and attributes to the anti-symmetric vibrations of O6 cages. The blue shift of this peak scales to ~2.4 cm−1 per 1 GPa of stress. Another strong feature showing considerable blue shift is seen in the vicinity of 640 cm−1 and corresponds to one of rhombohedral distortion related soft modes. A weak mode, not frequently reported, is seen at around 420 cm−1 and corresponds to translation-like motions of fixed O6 cages.

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Volume forces in simple metals

Canadian Journal of Physics ◽

10.1139/p79-257 ◽

1979 ◽

Vol 57 (11) ◽

pp. 1870-1883 ◽

Cited By ~ 19

Author(s):

S. H. Taole ◽

H. R. Glyde

Keyword(s):

Bulk Modulus ◽

Elastic Constants ◽

Alkali Metals ◽

Lattice Dynamic ◽

Second Order ◽

Reliable Estimate ◽

Dynamical Matrix ◽

Volume Dependence ◽

Long Wave ◽

Cauchy Relation

Within the local pseudopotential model taken to second order, the metallic energy, U, is a sum of a volume dependent and a structure dependent term. Only the second term, expressed as a volume independent, effective ion–ion interaction, is usually retained for lattice dynamic calculations. Here we firstly evaluate the contribution from the volume dependence of U to the longitudinal elastic constants c11and c12 and the bulk modulus B for a variety of models. This contribution, Δbs, which is due to the volume dependence of the screening, was identified by Wallace, Brovman and Kagan, Pethick, and by Finnis but its magnitude is in dispute. We find Δbs is important and very model dependent, ranging from −10 to−50% of B in the alkali metals and Al (but is +50% in Pb for one model) depending on both the pseudopotential and screening employed. Secondly, the usual dynamical matrix is generalized to incorporate this volume dependence. The volume effects are important for long wave phonons only and for most practical purposes may be neglected otherwise. The volume contributions to the pressure and the deviation of the Cauchy relation are also evaluated suggesting that the observed deviation of the Cauchy relation does not provide a reliable estimate of Δbs.

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The anomalous infra-red absorption of alkali metals and collective oscillations in small metal particles

Journal de Physique ◽

10.1051/jphys:01972003304037100 ◽

1972 ◽

Vol 33 (4) ◽

pp. 371-381 ◽

Cited By ~ 47

Author(s):

A. Meessen

Keyword(s):

Alkali Metals ◽

Metal Particles ◽

Infra Red ◽

Collective Oscillations ◽

Small Metal Particles

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Room Temperature Alkali Metal Reduction of Carbon Dioxide

10.26434/chemrxiv.12665336 ◽

2020 ◽

Author(s):

Lucas A. Freeman ◽

Akachukwu D. Obi ◽

Haleigh R. Machost ◽

Andrew Molino ◽

Asa W. Nichols ◽

...

Keyword(s):

Alkali Metal ◽

Alkali Metals ◽

Room Temperature ◽

Chemical Reduction ◽

Bond Cleavage ◽

Open Shell ◽

Metal Reduction ◽

One Pot ◽

Earth Abundant ◽

Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO2 to access useful CO2-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO2 and the MGE. Herein we report the first successful chemical reduction of CO2 at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO2 adduct (1) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO2)]n(M = Li, Na, K, 2-4) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M2(CAAC–CO2)]n (5-8). It is notable that these crystalline clusters of reduced CO2 may also be isolated via the “one-pot” reaction of free CO2 with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products 2-8 were investigated using a combination of experimental and theoretical methods.

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