Compute fragment properties from atomic coordinates and energies. Compare centers, masses, and reduced motion quickly. Save practical outputs for lab review and reporting tasks.
| Item | Example Value |
|---|---|
| Total System Energy | -152.010000 Hartree |
| Fragment A Energy | -76.002000 Hartree |
| Fragment B Energy | -76.001000 Hartree |
| Fragment A Coordinates | O,0.000000,0.000000,0.000000 / H,0.758000,0.000000,0.504000 / H,-0.758000,0.000000,0.504000 |
| Fragment B Coordinates | O,0.000000,0.000000,2.850000 / H,0.758000,0.000000,3.354000 / H,-0.758000,0.000000,3.354000 |
Gaussian molecular fragment calculation helps chemists inspect complex systems in smaller parts. It separates a large structure into meaningful fragments. Then it reports mass, charge balance, geometry relations, and energy behavior. This approach is useful for dimers, host guest systems, reaction paths, and weakly bound clusters.
A fragment study often begins with atomic coordinates from an optimized structure. Each fragment can contain several atoms. The calculator totals atomic masses and builds a fragment formula. It also finds the center of mass from weighted coordinates. That value helps compare how two fragments sit in space.
The separation between fragment centers gives a simple structural metric. A shorter distance may suggest tighter packing. The minimum atom to atom distance gives another quick check. It can reveal close contacts, possible clashes, or hydrogen bond regions. Radius of gyration adds shape insight because it measures spread around each fragment center.
Energy analysis is also important. When total system energy and fragment energies are known, the interaction energy can be estimated. Negative values suggest stabilization. Positive values suggest repulsion or an unfavorable arrangement. The calculator accepts Hartree, electron volt, kilojoule per mole, and kilocalorie per mole. It then converts interaction energy into several useful units.
Charge based screening can support interpretation. If both fragment charges are entered, the tool estimates a simple Coulombic term using center separation. This is not a full quantum result. Still, it offers a fast directional check during early review. Reduced mass is also reported. That value is useful in vibration, collision, and relative motion discussions.
Because fragment inputs may come from different workflows, the parser accepts either symbol plus coordinates or symbol, custom mass, and coordinates. That flexibility supports isotope checks and manual testing. It makes classroom examples easier to reproduce when exact masses or simplified coordinates are preferred.
This page is designed for quick practical work. Paste coordinates, enter energies, and submit. The result block appears above the form for fast reading. You can export a CSV summary or save a PDF copy. The example table shows the expected input style. The formula section explains the math clearly. The FAQ section answers common setup questions. Together, these parts create a compact lab ready reference for fragment based chemistry analysis.
Fragment mass: M = Σmi
Center of mass: Xcom = Σ(mixi)/Σmi, and the same rule applies for Y and Z.
Reduced mass: μ = (MA × MB) / (MA + MB)
Interaction energy: Eint = Etotal - (EA + EB)
Center distance: d = √[(x1-x2)² + (y1-y2)² + (z1-z2)²]
Radius of gyration: Rg = √[Σmiri² / Σmi]
Estimated Coulombic term: E ≈ 332.06371 × qA × qB / r
It measures fragment mass, formula, center of mass, radius of gyration, center separation, minimum atom distance, reduced mass, and interaction energy.
Yes. Use the format Symbol,mass,x,y,z. That lets you override the default periodic table mass for isotope checks or custom teaching examples.
Use one consistent distance unit across both fragments. The page assumes Angstrom style geometry for labels, so mixed units should be avoided.
The page subtracts the sum of fragment energies from the full system energy. A negative result suggests stabilization between the fragments.
No. It is only a simple electrostatic estimate based on fragment charges and center distance. It is useful for screening, not final interpretation.
Reduced mass helps describe relative fragment motion. It is useful in discussions about vibrations, collisions, and simple two body models.
The page stops that line and shows an error. You can fix the symbol or provide a custom mass in the five value format.
Yes. After a successful calculation, use the CSV button for spreadsheet work or the PDF button for a clean report copy.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.