Synchrotron-based high-pressure research in materials science Page: 4 of 13
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F 7UREDO .Fnlspcrlcmprsn etenteLEDCOPadATMCopct ds
a R mixe C C daaaefrATOMIC, u o u aeiecmaioteC fet
e s 10 d e0
e o: . ..I.
10' 100 I( 50.0 52.05 S40 560 5A 600 62-0 6.0 660 630 700
whh- Eonsidey a( e eV "it principa (eat nubrn V) upstel>4sae
FIGURE 2. Initial spectral comparisons between the LEDCOP and ATOMIC opacity codes.
cuaton aebingsidfoEDCOP toAO IC h LEDCOP lnsaoe6
eV areslihy shAe rmteAO I ausdeTOteqanu eec is sdi
E E 0
10 E
a lo' a
JO o OJO 0 52.0 5401 S60 $80 (0.0 6270 00.0 66.0 60.0 70.0
LECO0t0rdue h size0 ofte aabs.Th hiti not importanty fora0pciis
FIGURE 3. Final spectral comparisons between the LEDCOP and ATOMIC opacity codes.
a mixed SC/Cl database for ATOMIC, but for our baseline comparison, the CI effects
were removed from the LEDCOP database.
The second major discrepancy was the factor of 3 to 10 difference in the valleys
between the line peaks. This occured because of limitations in the LEDCOP database,
which considers all levels with principal quantum number n, but lumps the 1 > 4 states
together for the EOS and does not allow high n, high 1 transitions for states with n > 5
and 1 > 4. ATOMIC includes these transitions, with energies from 1 eV to 6 eV, and
all of them are broad, with large oscillator strengths. Since it was not possible to put
these transitions into LEDCOP, they were removed from the ATOMIC database for this
comparison. The modified results from the two codes are shown in Fig. 3a and Fig. 3b,
where agreement is now very good except for some lines at 63 eV and above 68 eV.
The remaining minor differences illustrate two of the reasons why the opacity cal-
culations are being shifted from LEDCOP to ATOMIC. The LEDCOP lines above 68
eV are slightly shifted from the ATOMIC values due to the quantum defect fits used in
LEDCOP to reduce the size of the database. The shift is not important for gray opacities,
but it does impact spectral comparisons. The missing lines at 63 eV were more serious.
A considerable amount of hand work was needed to build the LEDCOP databases and
these transitions were inadvertently omitted. The ATOMIC databases are much more
automated, reducing these types of errors. 1
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Synchrotron-based high-pressure research in materials science, article, Date Unknown; [Los Alamos, New Mexico]. (https://digital.library.unt.edu/ark:/67531/metadc927134/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.