TY - JOUR
T1 - Bragg's additivity rule and core and bond model studied by real-time TDDFT electronic stopping simulations: The case of water vapor
AU - Gu, Bin
AU - Muñoz-Santiburcio, Daniel
AU - Da Pieve, Fabiana
AU - Cleri, Fabrizio
AU - Artacho, Emilio
AU - Kohanoff, Jorge
PY - 2022/4
Y1 - 2022/4
N2 - The electronic stopping power (S
e
) of water vapor (H2O), hydrogen (H2) and oxygen (O2) gases for protons in a broad range of energies, centered in the Bragg peak, was calculated using real-time time-dependent density functional theory (rt-TDDFT) simulations with Gaussian basis sets. This was done for a kinetic energy of incident protons (E
k
) ranging from 1.56 keV/amu to 1.6 MeV/amu. S
e
was calculated as the average over geometrically pre-sampled short ion trajectories. The average S
e
(E
k
) values were found to rapidly converge with 25–30 pre-sampled, 2 nm-long ion trajectories. The rt-TDDFT S
e
(E
k
) curves were compared to experimental and SRIM data, and used to validate the Bragg's Additivity Rule (BAR). Discrepancies were analyzed in terms of basis set effects and omitted nuclear stopping at low energies. At variance with SRIM, we found that BAR is applicable to our rt-TDDFT simulations of 2H2 + O2 → 2H2O without scaling for E
k
> 40 keV/amu. The hydrogen and oxygen Core and Bond (CAB) contributions to electronic stopping were calculated and found to be slightly smaller than SRIM values as a result of a red-shift in our rt-TDDFT S
e
(E
k
) curves and a re-distribution of weights due to some bond contributions being neglected in SRIM.
AB - The electronic stopping power (S
e
) of water vapor (H2O), hydrogen (H2) and oxygen (O2) gases for protons in a broad range of energies, centered in the Bragg peak, was calculated using real-time time-dependent density functional theory (rt-TDDFT) simulations with Gaussian basis sets. This was done for a kinetic energy of incident protons (E
k
) ranging from 1.56 keV/amu to 1.6 MeV/amu. S
e
was calculated as the average over geometrically pre-sampled short ion trajectories. The average S
e
(E
k
) values were found to rapidly converge with 25–30 pre-sampled, 2 nm-long ion trajectories. The rt-TDDFT S
e
(E
k
) curves were compared to experimental and SRIM data, and used to validate the Bragg's Additivity Rule (BAR). Discrepancies were analyzed in terms of basis set effects and omitted nuclear stopping at low energies. At variance with SRIM, we found that BAR is applicable to our rt-TDDFT simulations of 2H2 + O2 → 2H2O without scaling for E
k
> 40 keV/amu. The hydrogen and oxygen Core and Bond (CAB) contributions to electronic stopping were calculated and found to be slightly smaller than SRIM values as a result of a red-shift in our rt-TDDFT S
e
(E
k
) curves and a re-distribution of weights due to some bond contributions being neglected in SRIM.
U2 - 10.1016/j.radphyschem.2022.109961
DO - 10.1016/j.radphyschem.2022.109961
M3 - Article
SN - 0969-806X
VL - 193
JO - Radiation Physics and Chemistry
JF - Radiation Physics and Chemistry
M1 - 109961
ER -