@User The reram symbol uses a verilog-AMS description, using Verilog-AMS in ngspice is very complex, you must build a new ngspice executable or library with the reram model linked in. For now i have added into xschem a symbol for the reram device with the correct (as far as i know) netlist format, but i definitely need some help for using this in ngspice simulations.

Thanks for the reply @User , can you please let me know what verilog-AMS description reram symbol uses? Unless you disclose all the details and procedure to add new ngspice executable or library, how the community members can understand and contribute. Just see I am unable to simulate with reram symbol, it is saying in .out file that "Error on line 9 or its substitute: y1 vout vdd rram2_model m=1 Unable to find definition of model 1 Simulation interrupted due to error!"

@Bhanprakash Goswami this is the main repository i used to build the xschem symbol: https://github.com/google/skywater-pdk-libs-sky130_fd_pr_reram