An ab Initio Study of Linear XH−HX Hydrogen Halide Anions
Bibliographic record
Abstract
This paper examines the stabilities of singly charged anions with the linear opposed dipole structures: FH−HF, ClH−HCl and BrH−HBr at MP2 and CCSD(T) levels. With 6-311+G(3df,2p) basis sets on Cl and Br and aug-cc-pvdz on H and F, MP2 structures were obtained for all three systems. Since the neutral dimers with opposed dipoles are unstable, the energies for the electron detachment processes were evaluated relative to separated free neutrals, viz.: XH−HX· - → e - + 2HX. At the CCSD(T) level these energies were 0.26 and 0.84 V for HCl and HBr, respectively, but the value for HF is negative. The addition of diffuse orbitals at the central point between the two H atoms lowered the energy and caused the H−H distance in the FH−HF species to increase. Also the excess electron moved into the diffuse orbitals and the species assumed a solvated electron structure, a finding which is in agreement with previous work. In contrast, for the HCl and HBr species the addition of diffuse orbitals had no significant effect. The optimized geometries, charge and spin distributions, and the adiabatic electron detachment energies all remained essentially unchanged. This result and other molecular parameters indicated that in the ClH−HCl and BrH−HBr anions the extra electrons were located in valence orbitals made up from the σ* orbitals of the two HX molecules. The nature of these orbitals was discussed. Since the dipole moment of the HCl.HCl neutral dimer is considered too small for formation of a dipole-bound anion state (as occurs with HF.HF), it is quite probable that HCl dimer anion observed experimentally is of the XH−HX· - type.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".