Questions tagged [vibrations]
Questions concerning molecular and solid vibrational modes.
63 questions
5 votes
1 answer
76 views
Kinetic rotational energy of a dis-rotational motion?
I'm interested in solving the eigenstates for a $\ce{H3C-NH3}$ molecule. I want to check into the dis-rotatory torsional vibration along the $\ce{C-N}$ axis, as in this scheme: I already know the ...
- 121
3 votes
0 answers
41 views
VASP vibrational calculation with IBRION=7 fail to converge?
I am trying to run a vibrational frequency calculation in VASP using IBRION=7 (I tried IBRION 5 as well). The system is a monolayer over the CsPbBr₃ (001) slab. In POSCAR I fixed all atoms of the slab ...
- 101
3 votes
0 answers
22 views
The best choice of the Extension Shell in the Partial Hessian Vibrational Analysis (PHVA)
I am interested in vibrational analysis (Hessian) for the QM part of a QM/MM system, with the MM part being frozen. This is (usually) done using the Partial Hessian Vibrational Analysis (PHVA). If I ...
- 763
3 votes
0 answers
36 views
Connection between nuclear Hessian and MO coefficient rotation matrix along normal coordinates
Are there any expressions that connect the nuclear Hessian of a molecule at the minimum of its PES to the rotation matrix of MO coefficients, which modifies MO coefficients during nuclear ...
- 71
2 votes
0 answers
49 views
Computing the vibrational frequencies with Newton's mechanics
I need to implement the computation of vibrational frequencies of molecules in RRHO approximation. I have already coded this computation - the Hessian matrix is recounted with my program to mass-...
- 596
6 votes
1 answer
173 views
What is the relationship between electron-phonon coupling and nonadiabatic effects?
We know that under the Born-Oppenheimer (BO) approximation, the motion of nuclei and electrons is decoupled. However, when there is a degeneracy between potential energy surfaces, the nonadiabatic ...
- 61
3 votes
0 answers
155 views
Obtain force constants from normal modes
I am trying to reproduce an QTAIM analysis by Foroutan-Nejad et al. (https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/chem.201402177). Instead of only looking into the equilibrium ...
- 331
3 votes
0 answers
69 views
Visualization of phonon modes in siesta
When I try to visualize phonon modes using vib2xsf utility in siesta (DFT code) for a nanowire system, the utility gives an error "Error reading real part of eigenvector 1 iat= ...
- 389
1 vote
1 answer
71 views
Algorithm for finding the v=1 state of an H2O molecule
In the context of simulating the dissociation dynamics of an H₂O molecule on a metal surface, what algorithm is employed for generating the initial state of a tri-atomic non-linear molecule, such as H₂...
- 147
6 votes
2 answers
456 views
How may I solve the radial Schrödinger equation?
I want to solve the radial Schrodinger equation for a Carbon atom with all six electrons. The equation I want to solve is for $r>0$: $$[\frac{-\hbar^2}{2m}\frac{\partial^2}{\partial r^2}+ \frac{\...
- 63
5 votes
0 answers
115 views
How does dimer and monomer zero point energy affect dissociation energy?
This paper by Xinchuan Huang et al. gives a calculation for the dissociation energy of a water dimer. The electronic dissociation energy (what they call $D_e$) is around 21 kJ/mol, and this is ...
- 1,332
4 votes
0 answers
64 views
Carbon Capture Research - Force Constants & Basis Sets
Greetings Matter Modeling, I'm researching carbon capture dynamics in the context of sorbent regeneration. The UN IPCC Net-Zero goal requires 75 Mt-CO₂/year captured by 2030. According to the IEA, we ...
- 111
6 votes
1 answer
191 views
Do conformations arise from vibrations?
Cross-posted on Chemistry SE. I was wondering how a molecule transforms from one conformation into another. Surely, since the conformations are separated by a potential barrier, some activation energy ...
- 221
7 votes
0 answers
258 views
How do you calculate a full quartic force field for anharmonic frequencies?
I am an experimental chemist interested in anharmonicity—I am particularly interested in how to calculate anharmonic frequencies. The method I have the most experience with is (generalised) second ...
- 495
5 votes
1 answer
82 views
Database on calculated molecular vibrations including coordination complexes?
Related to the question Are there dashboards displaying experimental properties of molecular materials? My question is: Are there any good, free, online databases on calculated vibrational modes of ...
- 1,526