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	4020	August 12, 2019
Welcome to the PSI4 Forum!	1	23389	July 16, 2015
Can a CC Computation Be Restarted?	3	19	March 31, 2025
TDDFT Calculation Crashes	4	34	March 27, 2025
Bug report psio	1	20	March 26, 2025
How Does Psi4 Handle Basis Set Cartesian vs. Spherical GTOs in Quantum Chemistry Calculations	4	42	March 25, 2025
Spin-orbital correction	4	39	March 22, 2025
CCSD calculation with energy('ccsd')	5	37	March 20, 2025
Segmentation fault in fisapt when using DFDirJ+CosX SAPT	0	11	March 19, 2025
Single point job stops over 65 atoms; no error message	1	33	March 13, 2025
DLPNO-CCSD(T) method feature-request	2	82	March 4, 2025
Out of memory using PCM model: Geom. optimization of lithiated ethylene carbonate Geometry Optimization	3	451	March 1, 2025
Def2-universal-jkfit and def2-tzvpp-ri bases? SAPT	0	35	March 1, 2025
Statically-linking Psi4 build	3	48	February 18, 2025
Investigating a chalcogen interaction with i-sapt SAPT	0	29	February 15, 2025
Challenges in Locating the Transition State for Meisenheimer Complex Formation in the SNAr Reaction of 4-Chloropyridine with Azide Anion Geometry Optimization	0	20	February 14, 2025
Error when using psi4/resp: Fatal Error: RHF: RHF reference is only for singlets SAPT	1	37	February 13, 2025
Colab GPU Accelerator Config build	0	34	February 9, 2025
UnboundLocalError for geometry optimization of Li4 with python module psi4 Geometry Optimization	2	31	February 3, 2025
Fractional occupation with PsiAPI	1	23	February 3, 2025
IOH augmented base	2	25	January 27, 2025
One electron Density Matrix diagonals don't sum to 1	9	102	January 22, 2025
Does Freeze Core also impact full La-group shells? Geometry Optimization	0	19	January 21, 2025
Excited states dipole moment	2	31	January 21, 2025
Gorling-Levy perturbation theory feature-request	0	18	January 18, 2025
Lmax exceed, cc-pv8z	3	61	January 13, 2025
DFT with a custom starting `Da` & `Db`	1	42	January 9, 2025
Calculating the first order electrostatic energy in the monomer basis using Psi4Numpy SAPT	5	860	December 28, 2024
Could Someone Give me Advice on Developing a New PsiCode Plugin?	0	28	December 26, 2024
PSA: Psi4 Installers Down	0	51	December 24, 2024

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…