GMX-SAXS-LEGACY(1)

✨ gmx-saxs-legacy ✨

okay so bestie, we're in the GROMACS manual rn and the page we're looking at is gmx-saxs-legacy 💖 grab a snack, this one's cute

💅 NAME 💅

gmx-saxs-legacy — compute small angle X-ray scattering spectra 🦋✨

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🎀 SYNOPSIS 🎀

gmx saxs-legacy [-f [<.xtc/.trr/...>]] [-s [<.tpr/.gro/...>]]
             [-n [<.ndx>]] [-d [<.dat>]] [-sq [<.xvg>]] [-b <time>]
             [-e <time>] [-dt <time>] [-xvg <enum>] [-ng <int>]
             [-startq <real>] [-endq <real>] [-energy <real>]

🌸 DESCRIPTION 🌸

so gmx saxs-legacy calculates SAXS structure factors for whatever index groups you hand it, and it does this based on Cromer's method. 🧚

and listen — both a topology file and a trajectory file are required. not one or the other. both. she's demanding like that 💀

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👑 OPTIONS 👑

🍓 Options to specify input files:

• -f [<.xtc/.trr/...>] (traj.xtc) — bestie this is your trajectory. it can be: xtc trr cpt gro g96 pdb tng h5md 🏃♀️
• -s [<.tpr/.gro/...>] (topol.tpr) — the structure + mass (db) file. formats: tpr gro g96 pdb brk ent 💖
• -n [<.ndx>] (index.ndx) — the index file. (Optional, so she's not gonna force your hand ✨)
• -d [<.dat>] (sfactor.dat) — a generic data file. (Optional too 🎀)

🌈 Options to specify output files:

• -sq [<.xvg>] (sq.xvg) — an xvgr/xmgr file 💅

⭐ Other options:

• -b <time> (0) — time of the first frame to read from the trajectory (default unit is ps) ⏰
• -e <time> (0) — time of the last frame to read from the trajectory (default unit is ps) ⏳
• -dt <time> (0) — only use a frame when t MOD dt = first time (default unit is ps) 🙈
• -xvg <enum> (xmgrace) — xvg plot formatting, and your choices are literally: xmgrace, xmgr, none 🎨
• -ng <int> (1) — number of groups to compute SAXS for 👯♀️
• -startq <real> (0) — starting q, in 1/nm 📏
• -endq <real> (60) — ending q, in 1/nm 📐
• -energy <real> (12) — energy of the incoming X-ray, in keV ⚡

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🦋 SEE ALSO 🦋

• gmx(1)

more info about GROMACS lives at <http://www.gromacs.org/> 👑

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💜 COPYRIGHT 💜

2026, GROMACS development team 🫶

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no cap, that's the whole page. go compute some spectra, you main character 🔥

and that's a wrap, babe — this was version 2026.4, dated Oct 02, 2026. slay, periodt 💅✨