Psi4 – Open-Source Quantum Chemistry

Topic	Replies	Views	Activity
Making Topics that Get Answered Most questions that are answered on the Psi4 Forums are answered by a small group of developers and powerusers. Their time and energy is divided between their own research, further Psi development, and helping users. Acc…	2	4037	August 12, 2019
Welcome to the PSI4 Forum!	1	23416	July 16, 2015
No exception thrown at unconverged geometry opt (geomeTRIC) Geometry Optimization	2	23	May 20, 2025
DFT First order hyperpolarizability (beta) feature-request	0	12	May 16, 2025
Failing convergence of Flexible Molecule - Back transformation failed Geometry Optimization	0	19	May 16, 2025
FREEZE_ALL_DIHEDRALS not valid	1	17	May 15, 2025
Extract force constants from python api?	2	31	May 12, 2025
Does Freeze Core also impact full La-group shells? Geometry Optimization	2	38	May 11, 2025
How do you install `gdma`?	1	25	May 7, 2025
Installation + enable gdma	4	637	May 7, 2025
Does Psi4 work with python 3.13?	2	39	April 29, 2025
Software source not found build	3	38	April 29, 2025
Why is Psi talking about "cc" when I asked for "cc-pVXZ"?	1	35	April 23, 2025
NBO analysis in PSI4 Psi4Education	3	1905	April 23, 2025
NMR calculation	1	37	April 22, 2025
Old versions of python	4	32	April 16, 2025
Psi4 "killed" during execution if too many basis/cartesian functions Geometry Optimization	0	22	April 15, 2025
Calculating properties from ESP on an isocontour of electronic density	0	13	April 14, 2025
CPHF MO gradients from scfgrad/response.cc do not match finite difference values	2	32	April 10, 2025
C_right_ and C_left_ at jk calculation	4	34	June 3, 2025
FSAPT requires a lot more memory than estimate SAPT	0	40	April 2, 2025
Can a CC Computation Be Restarted?	3	51	March 31, 2025
TDDFT Calculation Crashes	4	56	March 27, 2025
Bug report psio	2	27	March 26, 2025
How Does Psi4 Handle Basis Set Cartesian vs. Spherical GTOs in Quantum Chemistry Calculations	5	66	March 25, 2025
Spin-orbital correction	5	60	March 22, 2025
CCSD calculation with energy('ccsd')	6	57	March 20, 2025
Segmentation fault in fisapt when using DFDirJ+CosX SAPT	0	18	March 19, 2025
Single point job stops over 65 atoms; no error message	1	41	March 13, 2025
DLPNO-CCSD(T) method feature-request	3	137	March 4, 2025

Making Topics that Get Answered

Most questions that are answered on the Psi4 Forums are answered by a small group of developers and powerusers. Their time and energy is divided between their own research, further Psi development, and helping users. Acc…