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Proton vibrational dynamics in lithium imide investigated through incoherent inelastic and Compton neutron scattering
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10.1063/1.4767566
/content/aip/journal/jcp/137/20/10.1063/1.4767566
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/20/10.1063/1.4767566

Figures

Image of FIG. 1.
FIG. 1.

Measured raw spectra, S s (Q B , E), from sample “a” (lithium imide, dashed line), sample “b” (lithium amide, full line), and sample “c” (empty can, dotted-dashed line). All the spectra have been collected by the backscattering section of TOSCA-II at low temperature (T = 20 K). Plots have been vertically shifted for graphic reasons, namely, 0.055 arbitrary units for “b,” and 0.160 arbitrary units for “a.”

Image of FIG. 2.
FIG. 2.

Backscattering time-of-flight spectrum obtained by focusing individual detector spectra in the angular range between 150° and 165°: the feature at about 290 μs is the Li recoil peak, while those at about 338 μs and 360 μs are the recoil peaks of N and Al, respectively.

Image of FIG. 3.
FIG. 3.

Estimates of the proton-projected density of phonon states extracted from TOSCA-II inelastic neutron scattering measurements on Li2NH at T = 20 K: full line from the forward scattering detector banks, dashed line from the backscattering detector banks.

Image of FIG. 4.
FIG. 4.

Estimates of the proton-projected density of phonon states extracted from TOSCA-II inelastic neutron scattering measurements on LiNH2 at T = 20 K: full line from the forward scattering detector banks, dashed line from the backscattering detector banks.

Image of FIG. 5.
FIG. 5.

(a) n H(p) at T = 10 K, 150 K, 220 K, and 300 K reconstructed from the Gauss-Laguerre expansion with the coefficient listed in Table II; (b) n H(p) at the two extreme temperatures and their difference, with error bars.

Image of FIG. 6.
FIG. 6.

(a) n H(p) at all the investigated temperatures in a logarithmic scale enhancing the differences in the tails above p = 15 Å−1; (b) the same as in (a), but only for the two extreme temperatures, with error bars.

Image of FIG. 7.
FIG. 7.

Proton mean kinetic energy in lithium imide as a function of temperature obtained from: deep inelastic neutron scattering measurements (open black circles); H-projected density of phonon states measured at T = 20 K, via Eq. (4) (full blue lozenges); ab initio lattice dynamics simulations (full red squares). Red line is a guide for the eyes.

Image of FIG. 8.
FIG. 8.

Li and N mean kinetic energies in lithium imide as a function of temperature obtained from: deep inelastic neutron scattering measurements (Li: open black circles, N: open black squares); ab initio lattice dynamics simulations (Li: full red circles, N: full blue squares). Lines are guides for the eyes. Errors on N neutron data are smaller than symbols.

Tables

Generic image for table
Table I.

Experimental conditions of the IINS (a, b, c) and NCS (i, ii, iii, iv) measurements, where IPC stands for the integrated proton current of the ISIS neutron source.

Generic image for table
Table II.

Standard deviation, σ, of the longitudinal momentum distribution J(y) for H, and its mean kinetic energy, in Li2NH at the different temperatures investigated. The last two columns lists the expansion coefficient c 2 and c 3 related to the 4th-order and the 6th-order Hermite polynomials, respectively.

Generic image for table
Table III.

Standard deviations of the longitudinal momentum distribution J(y), for lithium and nitrogen and corresponding mean kinetic energies at the different temperatures investigated (see main text for details).

Generic image for table
Table IV.

Momentum standard deviations and mean kinetic energies for Li, N, and H as obtained from harmonic lattice dynamics (HLD) calculations, and from quantum molecular dynamics simulations (only at T = 300 K) relying on the use of the so-called “quantum colored noise thermostat” (QCNT) technique (see Refs. 21,33 for details).

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/content/aip/journal/jcp/137/20/10.1063/1.4767566
2012-11-28
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Proton vibrational dynamics in lithium imide investigated through incoherent inelastic and Compton neutron scattering
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/20/10.1063/1.4767566
10.1063/1.4767566
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