Qwen2.5-7B-GrapheneContact-QDoRA-CoT

A domain-specific language model fine-tuned for condensed matter physics, specifically graphene–metal contact resistance research. This 7B model, trained on only 64 question–answer pairs, outperforms a 235B-parameter model with open-book access under closed-book evaluation conditions.

Key Result

Model Parameters Condition Correct (✓) Partial (△) Wrong (✗) Accuracy
Base 7B 7B Open-book 9 17 4 30%
FT 7B (this model) 7B Closed-book 22 5 3 73%
Qwen3-235B 235B Open-book 18 9 3 60%

A fine-tuned 7B model with no access to the source paper outperforms a 33× larger model that receives the paper's content as a prompt.

Model Details

Model Description

  • Developed by: Junsu Park
  • Affiliation: Department of Physics and Photon Science, Gwangju Institute of Science and Technology (GIST), Korea
  • Base model: Qwen/Qwen2.5-7B-Instruct
  • Fine-tuning method: QDoRA (Quantized Weight-Decomposed Low-Rank Adaptation) + Chain-of-Thought reasoning
  • Language: English
  • License: Apache 2.0
  • Domain: Condensed matter physics — graphene–metal contact resistance (TLCD/TECD devices)

Model Sources

Uses

Direct Use

This model is designed to answer domain-specific questions about graphene–metal contact resistance, including device structure (TLCD/TECD), fabrication processes, theoretical models (Landauer, BTH), and experimental results. It serves as a personalized research assistant for this specific domain.

Out-of-Scope Use

This model is trained on a single research paper and should not be used for general scientific reasoning, other physics domains, or any task outside graphene–metal contact resistance research.

Training Details

Training Data

64 expert-crafted question–answer pairs from a single condensed matter physics paper, organized into five categories:

Category Description
Structure / Geometry TLCD vs TECD device structure, contact dimensions
Theory / Mechanism Landauer model, BTH model, current crowding
Numerical / Experimental Contact resistance values, TLM measurements
Fabrication Metal-on-bottom process, Cr/Au deposition
Novelty / Contribution First experimental verification of area-dependent Rc

Each answer includes Chain-of-Thought (CoT) reasoning with <think> and <final> tags.

Training Hyperparameters

Parameter Value
Adapter QDoRA (use_dora=True)
Rank (r) 64
Alpha (α) 128
Target modules q_proj, k_proj, v_proj, o_proj, gate_proj, up_proj, down_proj
Quantization 4-bit NF4, double quantization, bfloat16 compute
Max steps 80
Learning rate 5×10⁻⁴
Batch size 1 (gradient accumulation = 8, effective batch = 8)
Max sequence length 2048
Optimizer paged_adamw_8bit
Training time ~20 minutes
Training regime bf16 mixed precision

Hardware

Component Specification
GPU NVIDIA RTX 5090 (32 GB VRAM)
CPU AMD Threadripper PRO 5975WX (32 cores)
RAM 256 GB DDR4-3200 ECC
OS Ubuntu

Evaluation

30 expert-designed questions (distinct from training set) evaluated by the domain expert (first author of the source paper) using a three-tier rubric: ✓ (correct), △ (partial), ✗ (wrong).

Results by Category

Category Questions Base 7B FT 7B 235B
Structure / Geometry 4 1 3 3
Theory / Mechanism 10 4 8 7
Numerical / Experimental 6 2 5 4
Fabrication 6 1 4 2
Novelty / Contribution 4 1 2 2

Error Pattern Analysis

Each model exhibits qualitatively distinct failure modes:

  • Base 7B: Dominated by partial coverage (PC) — generates relevant but insufficiently specific responses
  • 235B: Dominated by over-extrapolation (OE) — fills knowledge gaps with plausible but incorrect scientific details
  • FT 7B (this model): Occasional directional reversal (DR) — correctly identifies relevant concepts but sometimes inverts their relationships

How to Get Started with the Model

from transformers import AutoModelForCausalLM, AutoTokenizer
from peft import PeftModel

# Load base model
base_model = AutoModelForCausalLM.from_pretrained(
    "Qwen/Qwen2.5-7B-Instruct",
    torch_dtype="auto",
    device_map="auto"
)
tokenizer = AutoTokenizer.from_pretrained(
    "pjspjs0987/Qwen2.5-7B-GrapheneContact-QDoRA-CoT"
)

# Load fine-tuned adapter
model = PeftModel.from_pretrained(
    base_model,
    "pjspjs0987/Qwen2.5-7B-GrapheneContact-QDoRA-CoT"
)

# Inference
messages = [
    {"role": "user", "content": "Why does increasing contact area reduce contact resistance in graphene-metal interfaces?"}
]
text = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(text, return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=512, temperature=0.7, top_p=0.9)
print(tokenizer.decode(outputs[0][inputs["input_ids"].shape[1]:], skip_special_tokens=True))

Citation

@article{park2026small,
  title={Small Data, Small Model, Superior Domain Accuracy: Fine-Tuning a 7B Language Model as a Condensed Matter Physics Expert with 64 Examples},
  author={Park, Junsu},
  year={2026},
  institution={Gwangju Institute of Science and Technology (GIST)}
}

Contact

  • Author: Junsu Park
  • Affiliation: GIST, Department of Physics and Photon Science
  • Hugging Face: pjspjs0987

Framework versions

  • PEFT 0.18.0
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